Chris Achard

Posted on Sep 4, 2019 • Originally published at twitter.com

ES6 Mini Crash Course: How to Write Modern JavaScript

#javascript #webdev #node

This was originally posted as a Twitter thread: https://twitter.com/chrisachard/status/1169223691122749440

Want to write javascript like a sane person?

🔥 Here's a mini crash course just for you 🔥

ES6+ JavaScript can actually be FUN to write!

(codesandbox links at the end)

1.

var is dead. Don't use var. 😐

(why? lexical scoping)

If the variable will CHANGE, use let

If the variable WON'T change, use const

2.

Arrow functions automatically bind this

So it will be what you think it should be 95% of the time

3.

If you leave the {} off of arrow functions, it returns automatically

You can leave the the () off around the params if there's only one

The different syntax can be a bit confusing - but you get used to it pretty fast

4.

You can define default values for function arguments now.

Super handy! 🎉

5.

With destructuring assignment, you can pull out specific values from objects or arrays

Commonly used in function signatures too - now you can have named parameters! 🎉🎉

6.

There's a new syntax for exporting and importing modules

You can export a single default value, and as many named values as you want from a module

(notice the use of destructuring assignment to import named values!)

7.

Get the "rest" of the values in an object or array with three dots ...

(AKA, the rest operator)

8.

Three dots can also be used to E-X-P-A-N-D an object or array into a new one

This is called the spread operator

(Yes - three dots is both rest and spread. They are different, though conceptually similar)

9.

Backticks can be used to wrap strings now, and are called "template literals"

Inside of backticks, you can use ${} to do string interpolation!

This is much easier than saying: "Hello " + name + "!"

10.

Most browsers now support these features natively! 🎉

(except for IE 😐)

Most of it works in node except for ES6 modules, but there's a way to fix that 👇

11.

Ok, but WHY is ES6+ JS better?

let/const scoped correctly
() => {} binds this correctly
destructuring assignment, ...rest and spread saves a bunch of typing

In short: it removes the hacks, does what you think it should, and less typing means fewer bugs.

Woo! 🎉

12.

Here's codesandbox links so you can explore:

var/let/const
https://codesandbox.io/s/es6-var-let-const-xz50k?fontsize=14

arrow functions
https://codesandbox.io/s/es6-arrow-function-gye29?fontsize=14

destructuring assignment
https://codesandbox.io/s/es6-destructuring-assignment-3cv3b?fontsize=14

import/export
https://codesandbox.io/s/es6-import-export-2q3px?fontsize=14

rest/spread & template literals
https://codesandbox.io/s/es6-rest-spread-template-literals-puli0?fontsize=14

This mini-crash-course was fun to write! I hope you enjoyed reading it 😁

If you liked it, you can find more by:

Following me on twitter: @chrisachard
Joining the newsletter: chrisachard.com

Thanks for reading!

Top comments (22)

Miguel Velez-White • Sep 6 '19

Chris, I was very impressed with your tutorial; but I was also quite dumbfounded. I'm basically a retread. I grew up in the era of mainframes, punch cards and COBOL. dBaseIII+ and IV reminded me how much I missed programming. However, I stayed on the admin/engineering track. Now we have DevOps (DevSecOps and DevNetOps in some places). I love the concept, but it's going to take a while before I can feel worthy enough to contribute anything. I thought that Javascript might be easy as I'd had a taste of JSON when I was doing PowerShell and .NET. You tutorial taught me alright. It taught me that I know NOTHING about javascript. I tried to follow along as best I could, but it was like trying to understand Integral Calculus again. Let's just say that I got my butt whooped and barely passed it all those years ago. Looks like I'm going to be sitting at the 'kiddies' table for a while as I try to learn these other dialects.

I love languages. I can even speak a few besides English. But right now, my heads filled with PowerShell, .NET, Terraform, Ansible, PowerCLI and so on. The further I get, the more I realize that I don't know and it can be frustrating; but at the end of the day, it really is still fun.

Do you by chance have a 'baby-primer' version of your class? I don't think that Javascript for Dummies could even help me right now. What I can relate to is your teaching style. You are a great communicator and your graphics for the examples are first rate. So I know that some day, I'll be able to understand your teachings a lot easier. For now, I'll take my dunce cap and go sit in the corner for a spell. Don't worry, I'm not giving up. It's all too much fun and if you and the community can be patient with a slowpoke like me, then I know that I'll make the grade - just a bit further down the road.

Meanwhile, if you ever need any help with VMware, or need a few virtual servers built somewhere, I offer my services gratis because I really want to learn from you.

LLAP,
Miguel (aka GulMiguel/Airwolf) :)

Chris Achard • Sep 6 '19 • Edited

Don't feel bad! I should have been more clear at the top that this is a good ES6 intro if you already know javascript. If you don't have much javascript experience yet, then a lot of this was probably quite confusing :)

I don't have a crash course for basic javascript yet - but I do have one planned! So you can look forward to that at some point.

One of the better resources I've found is a great free book called "Eloquent JavaScript": eloquentjavascript.net/ which is much more complete and beginner friendly.

This website (DEV) also has some great intro JS resources! You may have to search a bit to find them, but I know I've read some good ones here in the past.

I hope that helps some! Let me know if there's anything I can help with specifically, or if you're really stuck on something.

Oh! and the best advice I can give is to just play around! use codesandbox.io or codepen, and just start to experiment there and see how things go.

Good luck learning!

George • Sep 4 '19

Just remember that while you may be using const in a static context, it is still a mutable value.

Chris Achard • Sep 4 '19

Yes, good point (I actually almost included a warning in there, but too many warnings and it would no longer be a "mini" crash course 😂)

Here's a good example:

const myObject = { value: "abc" };
myObject.value = "123";
console.log(myObject); // {value: "123"}

So yes - if you really need immutability, then you have to use another library, like: github.com/immutable-js/immutable-js

Mehdi Raash • Sep 4 '19 • Edited

[...someVariable] it's actually spread attribute not operator.

Jan 13 '17

538

... are called spread attributes which, as the name represents, it allows an expression to be expanded.

var parts = ['two', 'three']
var numbers = ['one', ...parts, 'four', 'five']; // ["one", "two", "three", "four", "five"]

And in this case (I'm going to simplify it).

// Just assume we have an

…

Open Full Answer

Thanks for the recap

Oli Lalonde • Sep 11 '19

The term "spread attribute" is mostly used by React/JSX. Not that it really matters, but the most correct terminology would probably just be "spread syntax" (the ECMAScript spec only refers to it as "SpreadElement" in its grammar).

Chris Achard • Sep 4 '19

Interesting... heh - so, on that page it's called all four of these things:

Spread attribute
Spread operator
Spread syntax
Spread notation

... and it seems to all refer to the same thing :)

I've also found "official" docs calling it at least three of those things 🤣

Is there an actual "official, for real" source for what it's called?

Mehdi Raash • Sep 4 '19

I believe, operators need operand(s).

ECMA divided this topic to:

Arithmetic Operators
Comparison Operators
Logical Operators
Assignment Operators
Conditional Operators

Chris Achard • Sep 4 '19

Hm, interesting. Does the variable that the three dots are on not count as an operand? (I don't know what the formal definition is)

Mehdi Raash • Sep 4 '19

Somehow yes, but I think because this '...' thing introduced the time that syntactic sugar came up to JS so they tend to keep it as just helper syntax, some developers don't like it to be called as an operator because of other programming languages same debate.(some folks in this way would say one language has got more operators to another...:-))

Chris Achard • Sep 4 '19

Got, it (I think :) ). Interesting! I wasn't aware of the debate over the "operator" word. Thanks :)

Josh • Sep 16 '19 • Edited

This is a fantastic write-up of the core ES6 benefits! I just wanted to note that if performance is a concern for functions bound to this, then the handleEvent API carries infinitesimal overhead compared to the arrow function syntax and bind(this) calls within the constructor.

const clickCounter = {
  submit: 0,
  reset: 0,
  elements: {},

  // `this` will be `clickCounter`
  handleEvent({currentTarget, type}) {
    if (type === "click") {
      this.incrementClicks(currentTarget);
    }
  },

  // `this` will still be `clickCounter`!
  incrementClicks(currentTarget) {
    const {localName, type} = currentTarget;
    localName === "button" ? this[type]++ 
      : (this.elements[elTag(currentTarget)] || this.elements[elTag(currentTarget)] = 0)++;
  },

  elTag({localName, classList, id}) {return [
      localName,
      id ? `#${id}` : null,
      classList.length ? `.${[...classList].join(".")}` : null
    ].join("");
  }
}

// count ALL the clicks!!
document.addEventListener("click", clickCounter);

Magnus Buvarp • Sep 9 '19 • Edited

Quite late to the party here, but a cool thing to note regarding your point 5 is that you can also "selectively" deconstruct an array, that is, select only certain elements. Like this:

const array = [1, 2]
const [, second] = array
console.log(second) // 2

Or more advanced:

const array = [1, 2, 3, 4, 5, 6]
const [, second,, fourth,, sixth] = array
console.log(second, fourth, sixth) // 2 4 6

Chris Achard • Sep 9 '19

Yes, definitely! You can also put an underscore in the places you don't care about... eg:

const array = [1, 2, 3, 4]
const [_, second] = array
console.log(second) // 2

Alexander P. • Sep 4 '19

I just switched back to var...

Marc Hanisch • Dec 5 '19

Great article except the usage of var. I would not discourage it, as let is limited to the scope of braces whereas var is limited to the scope of the current this (function) context. Both have strengths.

Anderson • Sep 11 '19

Great article! Simple and useful, thank you!

Chris Achard • Sep 4 '19

Yep! There is also a solution that involves renaming files to .mjs and using --experimental-modules, but I find esm works really well in practice (and is easier)