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Charan Gutti
Charan Gutti

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How to Build, Test, and Check Your Own SDK Locally (Beginner-Friendly) in Javascript

#javascript #beginners #basic #explainlikeimfive

Building your own SDK (Software Development Kit) may sound complicated, but trust me—it’s actually simple. In this guide, we’ll walk through step by step how to:

  1. Build a small SDK.
  2. Test it in another project.
  3. Check which packages are installed.

And yes, we’ll keep it beginner-friendly with visuals. 🚀

🏗️ 1. Create the Project Structure

First, make a new folder called my-sdk.
Inside it, create two files:

my-sdk/
├── package.json
└── my-sdk.js
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File 1: package.json

{
  "name": "my-sdk",
  "version": "1.0.0",
  "main": "my-sdk.js"
}
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File 2: my-sdk.js

function sayHello() {
    return _internalHello();
}

function _internalHello() {
    return "Hello, World!";
}

module.exports = { sayHello };
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👉 package.json tells Node.js about your SDK (name, version, entry point).
👉 my-sdk.js is the logic—here, it just returns “Hello, World!”.

🔗 2. Install the SDK Locally

Open a terminal inside the my-sdk folder and run:

npm link
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This command makes your SDK available globally on your computer.
Think of it like: “Hey npm, please remember this package everywhere.”

🧪 3. Create a Test Project

Now, let’s test your SDK.

Create a different folder (e.g., test-project) and add a file called test.js:

test-project/
└── test.js
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File: test.js

const { sayHello } = require('my-sdk'); // Import your SDK

const message = sayHello();
console.log(message);
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▶️ 4. Link and Run the Test

Inside the test-project folder, run:

# Link your local SDK here
npm link my-sdk

# Run the test
node test.js
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✅ You should see:

Hello, World!
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🎉 Congrats! You just created and tested your very own SDK locally.

📦 5. How to See Installed Packages

Perfect question! After creating and testing your SDK, you might wonder:
“Which packages are installed right now?”

There are two main ways:

1. See ALL Packages Installed on Your Machine (Global)

Run this in any terminal:

npm list -g --depth=0
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  • -g = global packages (available everywhere).
  • --depth=0 = shows only top-level packages (not their dependencies).

2. See Packages for a Specific Project (Local)

Go to your project folder (the one with package.json) and run:

npm list --depth=0
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Example output:

my-test-project@1.0.0 /path/to/project
├── my-sdk@1.0.0
└── express@4.18.2
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👉 This tells you your project depends on my-sdk and express.

🖼️ Visual Flow

Here’s the big picture:

[ my-sdk ] --npm link--> [ global npm space ] --npm link my-sdk--> [ test-project ]
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So the flow is:

  1. Build your SDK (my-sdk).
  2. Link it globally (npm link).
  3. Connect it to your test project (npm link my-sdk).
  4. Run your test file (node test.js).

💡 Why This is Useful

  • You can develop faster without publishing to npm every time.
  • Any change in my-sdk.js reflects immediately in your test project.
  • You can easily check installed packages (global or local).

That’s it! You now know how to build, test, and inspect SDKs locally like a pro. 🚀

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