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    <title>DEV Community: Shaktijeet Sahoo</title>
    <description>The latest articles on DEV Community by Shaktijeet Sahoo (@deathcrafter).</description>
    <link>https://dev.to/deathcrafter</link>
    <image>
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      <title>DEV Community: Shaktijeet Sahoo</title>
      <link>https://dev.to/deathcrafter</link>
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    <language>en</language>
    <item>
      <title>#wecode Landing Page - WeCoded Challenge March 2025</title>
      <dc:creator>Shaktijeet Sahoo</dc:creator>
      <pubDate>Sat, 08 Mar 2025 04:42:06 +0000</pubDate>
      <link>https://dev.to/deathcrafter/wecode-landing-page-wecoded-challenge-march-2025-nci</link>
      <guid>https://dev.to/deathcrafter/wecode-landing-page-wecoded-challenge-march-2025-nci</guid>
      <description>&lt;p&gt;&lt;em&gt;This is a submission for the &lt;a href="https://dev.to/challenges/wecoded"&gt;WeCoded Challenge&lt;/a&gt;: Celebrate in Code&lt;/em&gt;&lt;/p&gt;

&lt;h2&gt;
  
  
  My WeCoded Landing Page
&lt;/h2&gt;

&lt;p&gt;On the forefront, I have incorporated a landing that covers a number of people, from different genders, races and religions. The idea is to let people feel welcome, and united, the first step to inclusivity.&lt;/p&gt;

&lt;blockquote&gt;
&lt;p&gt;NOTE: For now, if you go through the code, only male and female genders are used as those are the designs from &lt;a href="https://www.humaaans.com/" rel="noopener noreferrer"&gt;Humaaans&lt;/a&gt; but these can be updated using more inclusive designs.&lt;/p&gt;
&lt;/blockquote&gt;

&lt;p&gt;The later sections are ripped off from the &lt;a href="http://dev.to/wecoded"&gt;current landing page&lt;/a&gt;, with an addition of &lt;strong&gt;Winners&lt;/strong&gt; section as we have a challenge this year.&lt;/p&gt;

&lt;h2&gt;
  
  
  Demo
&lt;/h2&gt;

&lt;p&gt;&lt;iframe src="https://stackblitz.com/edit/stackblitz-starters-546xj2t9?embed=1&amp;amp;file=index.html&amp;amp;hideExplorer=1&amp;amp;view=preview" width="100%" height="500"&gt;
&lt;/iframe&gt;
&lt;/p&gt;

&lt;blockquote&gt;
&lt;p&gt;NOTE: Due to an issue with Tailwind being a native module, the app cannot be bootstrapped in StackBlitz or CodePen, so this is an embedded iframe that links &lt;a href="https://deathcrafter.github.io/wecoded-landing" rel="noopener noreferrer"&gt;https://deathcrafter.github.io/wecoded-landing&lt;/a&gt;.&lt;/p&gt;
&lt;/blockquote&gt;

&lt;h2&gt;
  
  
  How I Built It
&lt;/h2&gt;

&lt;p&gt;The following technologies and assets are used to make the landing:&lt;/p&gt;

&lt;ul&gt;
&lt;li&gt;React (Vite/TS)&lt;/li&gt;
&lt;li&gt;TailwindCSS&lt;/li&gt;
&lt;li&gt;[Asset] Humaaans Illustration Set (by &lt;a href="https://twitter.com/pablostanley" rel="noopener noreferrer"&gt;Pablo Stanley&lt;/a&gt;)&lt;/li&gt;
&lt;li&gt;[Asset] Illustrations from &lt;a href="https://freepik.com" rel="noopener noreferrer"&gt;Freepik&lt;/a&gt;
&lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;The app is hosted on Github Pages, with the demo embedded in StackBlitz. For better experience, go to the site: &lt;a href="https://deathcrafter.github.io/wecoded-landing" rel="noopener noreferrer"&gt;https://deathcrafter.github.io/wecoded-landing&lt;/a&gt;&lt;/p&gt;

&lt;h5&gt;
  
  
  Repository:
&lt;/h5&gt;


&lt;div class="ltag-github-readme-tag"&gt;
  &lt;div class="readme-overview"&gt;
    &lt;h2&gt;
      &lt;img src="https://media2.dev.to/dynamic/image/width=800%2Cheight=%2Cfit=scale-down%2Cgravity=auto%2Cformat=auto/https%3A%2F%2Fassets.dev.to%2Fassets%2Fgithub-logo-5a155e1f9a670af7944dd5e12375bc76ed542ea80224905ecaf878b9157cdefc.svg" alt="GitHub logo"&gt;
      &lt;a href="https://github.com/deathcrafter" rel="noopener noreferrer"&gt;
        deathcrafter
      &lt;/a&gt; / &lt;a href="https://github.com/deathcrafter/wecoded-landing" rel="noopener noreferrer"&gt;
        wecoded-landing
      &lt;/a&gt;
    &lt;/h2&gt;
    &lt;h3&gt;
      
    &lt;/h3&gt;
  &lt;/div&gt;
  &lt;div class="ltag-github-body"&gt;
    
&lt;div id="readme" class="md"&gt;
&lt;div class="markdown-heading"&gt;
&lt;h1 class="heading-element"&gt;React + TypeScript + Vite&lt;/h1&gt;
&lt;/div&gt;
&lt;p&gt;This template provides a minimal setup to get React working in Vite with HMR and some ESLint rules.&lt;/p&gt;
&lt;p&gt;Currently, two official plugins are available:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;
&lt;a href="https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-react/README.md" rel="noopener noreferrer"&gt;@vitejs/plugin-react&lt;/a&gt; uses &lt;a href="https://babeljs.io/" rel="nofollow noopener noreferrer"&gt;Babel&lt;/a&gt; for Fast Refresh&lt;/li&gt;
&lt;li&gt;
&lt;a href="https://github.com/vitejs/vite-plugin-react-swc" rel="noopener noreferrer"&gt;@vitejs/plugin-react-swc&lt;/a&gt; uses &lt;a href="https://swc.rs/" rel="nofollow noopener noreferrer"&gt;SWC&lt;/a&gt; for Fast Refresh&lt;/li&gt;
&lt;/ul&gt;
&lt;div class="markdown-heading"&gt;
&lt;h2 class="heading-element"&gt;Expanding the ESLint configuration&lt;/h2&gt;
&lt;/div&gt;
&lt;p&gt;If you are developing a production application, we recommend updating the configuration to enable type-aware lint rules:&lt;/p&gt;
&lt;div class="highlight highlight-source-js notranslate position-relative overflow-auto js-code-highlight"&gt;
&lt;pre&gt;&lt;span class="pl-k"&gt;export&lt;/span&gt; &lt;span class="pl-k"&gt;default&lt;/span&gt; &lt;span class="pl-s1"&gt;tseslint&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-en"&gt;config&lt;/span&gt;&lt;span class="pl-kos"&gt;(&lt;/span&gt;&lt;span class="pl-kos"&gt;{&lt;/span&gt;
  &lt;span class="pl-c1"&gt;extends&lt;/span&gt;: &lt;span class="pl-kos"&gt;[&lt;/span&gt;
    &lt;span class="pl-c"&gt;// Remove ...tseslint.configs.recommended and replace with this&lt;/span&gt;
    ...&lt;span class="pl-s1"&gt;tseslint&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;configs&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;recommendedTypeChecked&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
    &lt;span class="pl-c"&gt;// Alternatively, use this for stricter rules&lt;/span&gt;
    ...&lt;span class="pl-s1"&gt;tseslint&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;configs&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;strictTypeChecked&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
    &lt;span class="pl-c"&gt;// Optionally, add this for stylistic rules&lt;/span&gt;
    ...&lt;span class="pl-s1"&gt;tseslint&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;configs&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;stylisticTypeChecked&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
  &lt;span class="pl-kos"&gt;]&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
  &lt;span class="pl-c1"&gt;languageOptions&lt;/span&gt;: &lt;span class="pl-kos"&gt;{&lt;/span&gt;
    &lt;span class="pl-c"&gt;// other options...&lt;/span&gt;
    &lt;span class="pl-c1"&gt;parserOptions&lt;/span&gt;: &lt;span class="pl-kos"&gt;{&lt;/span&gt;
      &lt;span class="pl-c1"&gt;project&lt;/span&gt;: &lt;span class="pl-kos"&gt;[&lt;/span&gt;&lt;span class="pl-s"&gt;'./tsconfig.node.json'&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt; &lt;span class="pl-s"&gt;'./tsconfig.app.json'&lt;/span&gt;&lt;span class="pl-kos"&gt;]&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
      &lt;span class="pl-c1"&gt;tsconfigRootDir&lt;/span&gt;: &lt;span class="pl-k"&gt;import&lt;/span&gt;&lt;span class="pl-kos"&gt;.&lt;/span&gt;meta&lt;span class="pl-kos"&gt;.&lt;/span&gt;&lt;span class="pl-c1"&gt;dirname&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
    &lt;span class="pl-kos"&gt;}&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
  &lt;span class="pl-kos"&gt;}&lt;/span&gt;&lt;span class="pl-kos"&gt;,&lt;/span&gt;
&lt;span class="pl-kos"&gt;}&lt;/span&gt;&lt;span class="pl-kos"&gt;)&lt;/span&gt;&lt;/pre&gt;

&lt;/div&gt;
&lt;p&gt;You can also…&lt;/p&gt;
&lt;/div&gt;
  &lt;/div&gt;
  &lt;div class="gh-btn-container"&gt;&lt;a class="gh-btn" href="https://github.com/deathcrafter/wecoded-landing" rel="noopener noreferrer"&gt;View on GitHub&lt;/a&gt;&lt;/div&gt;
&lt;/div&gt;


&lt;h5&gt;
  
  
  Aspects Covered:
&lt;/h5&gt;

&lt;ol&gt;
&lt;li&gt;Look and feel.&lt;/li&gt;
&lt;li&gt;Functionality.&lt;/li&gt;
&lt;/ol&gt;

&lt;h5&gt;
  
  
  Aspects Not covered (I am a bit short on time):
&lt;/h5&gt;

&lt;ol&gt;
&lt;li&gt;Responsiveness&lt;/li&gt;
&lt;li&gt;ARIA-based accessibility.&lt;/li&gt;
&lt;li&gt;Small things like navbar and footer as I felt like those are supposed to be handled by the platform, e.g. would be identical to the one in primary site.&lt;/li&gt;
&lt;/ol&gt;

</description>
      <category>wecoded</category>
      <category>devchallenge</category>
      <category>webdev</category>
      <category>react</category>
    </item>
    <item>
      <title>Why Aggregation in MongoDB</title>
      <dc:creator>Shaktijeet Sahoo</dc:creator>
      <pubDate>Fri, 07 Mar 2025 02:14:31 +0000</pubDate>
      <link>https://dev.to/deathcrafter/why-aggregation-in-mongodb-152c</link>
      <guid>https://dev.to/deathcrafter/why-aggregation-in-mongodb-152c</guid>
      <description>&lt;p&gt;I have seen a lot of developers start with &lt;code&gt;.find()&lt;/code&gt; when working with MongoDB and stick to that. It's not inherently bad, as it's simple nature gives a simple and fluid head start, but sticking to that as you move is what I am not a fan of.&lt;/p&gt;

&lt;p&gt;Before jumping in, let's get things out of the way. &lt;code&gt;find()&lt;/code&gt; is faster than &lt;code&gt;aggregate()&lt;/code&gt; in general. If you are running a simple query, on a collection with limited documents, go with &lt;code&gt;find()&lt;/code&gt;. For example (with &lt;strong&gt;mongoose&lt;/strong&gt;, a JavaScript library that works as a ODM driver for MongoDB in node)):&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight typescript"&gt;&lt;code&gt;&lt;span class="c1"&gt;// .find()&lt;/span&gt;
&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;findResults&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="k"&gt;await&lt;/span&gt; &lt;span class="nx"&gt;BookModel&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;find&lt;/span&gt;&lt;span class="p"&gt;({&lt;/span&gt;&lt;span class="na"&gt;author&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;John Doe&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;});&lt;/span&gt;

&lt;span class="c1"&gt;// .aggregate()&lt;/span&gt;
&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;aggrResults&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="k"&gt;await&lt;/span&gt; &lt;span class="nx"&gt;BookModel&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;aggregate&lt;/span&gt;&lt;span class="p"&gt;([&lt;/span&gt;
    &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="na"&gt;$match&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="na"&gt;author&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;John Doe&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
&lt;span class="p"&gt;]);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;If you run the above app, you'll have a noticeable time difference (depends on the collection size), where aggregation takes more time than find.&lt;/p&gt;

&lt;p&gt;But that is not the reason I am writing this article, obviously. The problem with find comes in when we want to perform post-processing on the data. For example, after finding results you want to group them based on some parameter. Let's first weave an example:&lt;/p&gt;

&lt;h6&gt;
  
  
  Data
&lt;/h6&gt;



&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight json"&gt;&lt;code&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"The Silent Patient"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Alex Michaelides"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.3&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"The Maidens"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Alex Michaelides"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.0&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Ares"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Alex Michaelides"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;3.9&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"1984"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"George Orwell"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.7&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Animal Farm"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"George Orwell"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.5&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Homage to Catalonia"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"George Orwell"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.2&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Norwegian Wood"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Haruki Murakami"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.4&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Kafka on the Shore"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Haruki Murakami"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.6&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"1Q84"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Haruki Murakami"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.1&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Killing Commendatore"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Haruki Murakami"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.0&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Down and Out in Paris and London"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"George Orwell"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.3&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt;&lt;span class="w"&gt;
    &lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="nl"&gt;"name"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Hard-Boiled Wonderland and the End of the World"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"author"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="s2"&gt;"Haruki Murakami"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="nl"&gt;"rating"&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt;&lt;span class="w"&gt; &lt;/span&gt;&lt;span class="mf"&gt;4.2&lt;/span&gt;&lt;span class="p"&gt;}&lt;/span&gt;&lt;span class="w"&gt;
&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;&lt;span class="w"&gt;
&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;h6&gt;
  
  
  With &lt;em&gt;find()&lt;/em&gt;
&lt;/h6&gt;



&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight typescript"&gt;&lt;code&gt;&lt;span class="c1"&gt;// .find()&lt;/span&gt;
&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;findResults&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="k"&gt;await&lt;/span&gt; &lt;span class="nx"&gt;BookModel&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;find&lt;/span&gt;&lt;span class="p"&gt;();&lt;/span&gt;
&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;byAuthor&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="nx"&gt;findResults&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;reduce&lt;/span&gt;&lt;span class="p"&gt;((&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="o"&gt;=&amp;gt;&lt;/span&gt; &lt;span class="p"&gt;({&lt;/span&gt;
    &lt;span class="p"&gt;...&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;author&lt;/span&gt;&lt;span class="p"&gt;]:&lt;/span&gt; &lt;span class="p"&gt;[...(&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;author&lt;/span&gt; &lt;span class="o"&gt;??&lt;/span&gt; &lt;span class="p"&gt;[]),&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt;
&lt;span class="p"&gt;}));&lt;/span&gt;
&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;byRating&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="nx"&gt;findResults&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;reduce&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="o"&gt;=&amp;gt;&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;rating&lt;/span&gt; &lt;span class="o"&gt;&amp;gt;&lt;/span&gt; &lt;span class="mi"&gt;4&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;?&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;...&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="na"&gt;highRated&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[...&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;highRated&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;}&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;rating&lt;/span&gt; &lt;span class="o"&gt;&amp;lt;&lt;/span&gt; &lt;span class="mi"&gt;2&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;?&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;...&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="na"&gt;lowRated&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[...&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;lowRated&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;}&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="na"&gt;midRated&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[...&lt;/span&gt;&lt;span class="nx"&gt;acc&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nx"&gt;midRated&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;r&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="nx"&gt;highRated&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[],&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="nx"&gt;lowRated&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[],&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="err"&gt; &lt;/span&gt; &lt;span class="nx"&gt;midRated&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[],&lt;/span&gt;
&lt;span class="err"&gt; &lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
&lt;span class="p"&gt;);&lt;/span&gt;

&lt;span class="nx"&gt;console&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;log&lt;/span&gt;&lt;span class="p"&gt;({&lt;/span&gt; &lt;span class="nx"&gt;byAuthor&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;byRating&lt;/span&gt; &lt;span class="p"&gt;});&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;h6&gt;
  
  
  With &lt;em&gt;.aggregate()&lt;/em&gt;
&lt;/h6&gt;



&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight typescript"&gt;&lt;code&gt;&lt;span class="c1"&gt;// .aggregate()&lt;/span&gt;
&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;aggrResults&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="k"&gt;await&lt;/span&gt; &lt;span class="nx"&gt;BookModel&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;aggregate&lt;/span&gt;&lt;span class="p"&gt;([&lt;/span&gt;
    &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="na"&gt;$facet&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="na"&gt;byAuthors&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[&lt;/span&gt;
                &lt;span class="p"&gt;{&lt;/span&gt;
                    &lt;span class="na"&gt;$group&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                        &lt;span class="na"&gt;_id&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$author&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
                        &lt;span class="na"&gt;books&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;$push&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$$ROOT&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
                    &lt;span class="p"&gt;}&lt;/span&gt;
                &lt;span class="p"&gt;},&lt;/span&gt;
                &lt;span class="p"&gt;{&lt;/span&gt;
                    &lt;span class="na"&gt;$group&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                        &lt;span class="na"&gt;_id&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="kc"&gt;null&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
                        &lt;span class="na"&gt;byAuthor&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;$push&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;k&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$_id&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="na"&gt;v&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$books&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt; &lt;span class="p"&gt;}&lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
                    &lt;span class="p"&gt;}&lt;/span&gt;
                &lt;span class="p"&gt;},&lt;/span&gt;
                &lt;span class="p"&gt;{&lt;/span&gt;
                    &lt;span class="na"&gt;$project&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                        &lt;span class="na"&gt;_id&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="mi"&gt;0&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
                        &lt;span class="na"&gt;byAuthor&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;$arrayToObject&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$byAuthor&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
                    &lt;span class="p"&gt;}&lt;/span&gt;
                &lt;span class="p"&gt;}&lt;/span&gt;
            &lt;span class="p"&gt;],&lt;/span&gt;
            &lt;span class="na"&gt;byRating&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[&lt;/span&gt;
                &lt;span class="p"&gt;{&lt;/span&gt;
                    &lt;span class="na"&gt;$group&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                        &lt;span class="na"&gt;_id&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                            &lt;span class="na"&gt;$switch&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                                &lt;span class="na"&gt;branches&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[&lt;/span&gt;
                                    &lt;span class="p"&gt;{&lt;/span&gt;
                                        &lt;span class="na"&gt;case&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                                            &lt;span class="na"&gt;$gte&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$rating&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="mi"&gt;4&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt;
                                        &lt;span class="p"&gt;},&lt;/span&gt;
                                        &lt;span class="na"&gt;then&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;highRated&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;
                                    &lt;span class="p"&gt;},&lt;/span&gt;
                                    &lt;span class="p"&gt;{&lt;/span&gt;
                                        &lt;span class="na"&gt;case&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                                            &lt;span class="na"&gt;$lte&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$rating&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="mi"&gt;2&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt;
                                        &lt;span class="p"&gt;},&lt;/span&gt;
                                        &lt;span class="na"&gt;then&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;lowRated&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;
                                    &lt;span class="p"&gt;},&lt;/span&gt;
                                &lt;span class="p"&gt;],&lt;/span&gt;
                                &lt;span class="na"&gt;default&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;midRated&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
                            &lt;span class="p"&gt;}&lt;/span&gt;
                        &lt;span class="p"&gt;},&lt;/span&gt;
                        &lt;span class="na"&gt;books&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;$push&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$$ROOT&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
                    &lt;span class="p"&gt;}&lt;/span&gt;
                &lt;span class="p"&gt;},&lt;/span&gt;
                &lt;span class="p"&gt;{&lt;/span&gt;
                    &lt;span class="na"&gt;$group&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                        &lt;span class="na"&gt;_id&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="kc"&gt;null&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
                        &lt;span class="na"&gt;byRating&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;$push&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;k&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$_id&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="na"&gt;v&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$books&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt; &lt;span class="p"&gt;}&lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
                    &lt;span class="p"&gt;},&lt;/span&gt;
                &lt;span class="p"&gt;},&lt;/span&gt;
                &lt;span class="p"&gt;{&lt;/span&gt;
                    &lt;span class="na"&gt;$project&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
                        &lt;span class="na"&gt;_id&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="mi"&gt;0&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
                        &lt;span class="na"&gt;byRating&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt; &lt;span class="na"&gt;$arrayToObject&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$byRating&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt; &lt;span class="p"&gt;},&lt;/span&gt;
                    &lt;span class="p"&gt;}&lt;/span&gt;
                &lt;span class="p"&gt;}&lt;/span&gt;
            &lt;span class="p"&gt;]&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
&lt;span class="p"&gt;]);&lt;/span&gt;

&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="p"&gt;[{&lt;/span&gt; &lt;span class="nx"&gt;byAuthor&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nx"&gt;byRating&lt;/span&gt; &lt;span class="p"&gt;}]&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="nx"&gt;aggrResult&lt;/span&gt;&lt;span class="p"&gt;;&lt;/span&gt; &lt;span class="c1"&gt;// assuming the everything went right&lt;/span&gt;

&lt;span class="nx"&gt;console&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;log&lt;/span&gt;&lt;span class="p"&gt;({&lt;/span&gt; &lt;span class="na"&gt;byAuthor&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="nx"&gt;byAuthor&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="mi"&gt;0&lt;/span&gt;&lt;span class="p"&gt;],&lt;/span&gt; &lt;span class="na"&gt;byRating&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="nx"&gt;byRating&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="mi"&gt;0&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt; &lt;span class="p"&gt;});&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;blockquote&gt;
&lt;p&gt;📝 I am not including the results as they can be guessed.&lt;/p&gt;
&lt;/blockquote&gt;

&lt;p&gt;So, I gave an example that makes aggregation looks complicated. Why go to such length when you can just &lt;em&gt;&lt;strong&gt;find&lt;/strong&gt;&lt;/em&gt; it and then go about your day? Well, as I said, in the intro for simple use cases, like this one, with 10 documents in your collection, always &lt;code&gt;find()&lt;/code&gt; it.&lt;/p&gt;

&lt;p&gt;Let's complicate the example a bit, where you have a author collection and you want to bring in data from there as well. Now, if you are used to &lt;strong&gt;mongoose&lt;/strong&gt;, you can recall a nifty feature called &lt;code&gt;.populate()&lt;/code&gt;.&lt;/p&gt;

&lt;p&gt;So our example becomes:&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight typescript"&gt;&lt;code&gt;&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;findResults&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="k"&gt;await&lt;/span&gt; &lt;span class="nx"&gt;BookModel&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;find&lt;/span&gt;&lt;span class="p"&gt;().&lt;/span&gt;&lt;span class="nf"&gt;limit&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="mi"&gt;1000&lt;/span&gt;&lt;span class="p"&gt;).&lt;/span&gt;&lt;span class="nf"&gt;populate&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;author&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt;
&lt;span class="c1"&gt;// ... all the post-processing stuff&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;&lt;strong&gt;Day 1&lt;/strong&gt;: All good. Never better.&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;Day 2&lt;/strong&gt;: Now you have a million documents.&lt;/p&gt;

&lt;p&gt;What changes is that you make an API call, binge watch One Piece and then come back to a meet a loading screen.&lt;/p&gt;

&lt;p&gt;Let me explain why: The &lt;code&gt;populate()&lt;/code&gt; function in &lt;strong&gt;mongoose&lt;/strong&gt; makes a query for every book in your document to get it's author by id. So your one &lt;code&gt;.find().populate("author")&lt;/code&gt; actually runs 1001 queries. &lt;em&gt;Without the post-processing you are going to apply, i.e. &lt;strong&gt;1000*n&lt;/strong&gt; operations. And God forbid you have more relational fields that you want to populate.&lt;/em&gt;&lt;/p&gt;

&lt;p&gt;What shines here is &lt;code&gt;aggregate()&lt;/code&gt;.&lt;/p&gt;

&lt;p&gt;We run:&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight typescript"&gt;&lt;code&gt;&lt;span class="kd"&gt;const&lt;/span&gt; &lt;span class="nx"&gt;aggrResults&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="k"&gt;await&lt;/span&gt; &lt;span class="nx"&gt;BookModel&lt;/span&gt;&lt;span class="p"&gt;.&lt;/span&gt;&lt;span class="nf"&gt;aggregate&lt;/span&gt;&lt;span class="p"&gt;([&lt;/span&gt;
    &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="na"&gt;$limit&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="mi"&gt;1000&lt;/span&gt;
    &lt;span class="p"&gt;},&lt;/span&gt;
    &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="na"&gt;$lookup&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="na"&gt;from&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;authors&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
            &lt;span class="na"&gt;localField&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;author&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
            &lt;span class="na"&gt;foreignField&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;$_id&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
            &lt;span class="na"&gt;as&lt;/span&gt;&lt;span class="p"&gt;:&lt;/span&gt; &lt;span class="dl"&gt;"&lt;/span&gt;&lt;span class="s2"&gt;author&lt;/span&gt;&lt;span class="dl"&gt;"&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="p"&gt;},&lt;/span&gt;
    &lt;span class="c1"&gt;// ... rest of your pipelines&lt;/span&gt;
&lt;span class="p"&gt;])&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;Now, a single query runs. &lt;strong&gt;And it is faster than .find().populate("author")&lt;/strong&gt;. And we don't have to post process the data. We are served on a silver plate and then fed with a silver spoon.&lt;/p&gt;

&lt;p&gt;And this is just me touching the surface. Quoting Sir Isaac Newton, "What we know is a drop, what we don't know is an ocean." (from Dark, ofc)&lt;/p&gt;

&lt;p&gt;But before you jump into &lt;code&gt;aggregation()&lt;/code&gt;-ing everything, let me let you know of the caveats:&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;You have to be extremely careful with the limits of your MongoDB server. Aggregation, while handy, requires more resources to run than find.&lt;/li&gt;
&lt;li&gt;In case you are using corporate managed MongoDB instances, like Atlas, you have to be careful about pricing, as prices spike up when you run resource expensive queries.&lt;/li&gt;
&lt;li&gt;This extends point 1: If you have a locally setup server, you must keep in mind the memory allocated to the process/server, or your deployment will crash processing while large queries.&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;With that out of the way, get to replacing your complex &lt;code&gt;find()&lt;/code&gt;s with &lt;code&gt;aggregate()&lt;/code&gt;.&lt;/p&gt;

&lt;p&gt;I will cover more of aggregation in details in my following writeups.&lt;/p&gt;

&lt;blockquote&gt;
&lt;p&gt;📝 Thank you for reading till the end. I am open to criticisms, constructive or otherwise, as this is my first blog. Please help me to get better.&lt;/p&gt;
&lt;/blockquote&gt;

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      <category>webdev</category>
      <category>mongodb</category>
      <category>node</category>
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