recommended typescript config for node 8

Question

What is the recommended config for typescript if I want to ue the compiled sources with node 8?

most tutorials use the following tsconig.json:

{   "compilerOptions": {     "target": "es6",     "module": "commonjs"   } } 

But now I figured out, that not all available features are supported. For example ['foo'].includes('bar') throws the error: Property 'includes' does not exist on type 'string[]'.

I found an issue that addresses this problem. The solution is to use the lib es7. I could overwrite the default libs: "lib": ["es7"]

But I'm not sure if this is the best config for node 8 - are there more features which are not supported by that lib? are there to much features defined?

So my question is: What are the best configurations for target, lib and module if I want to use node 8?

Answer 1

As of Node.js 8.10.0, 100% of ES2017 is supported. If you know that you are targeting that version or newer, the optimal config would look like this:

• "module": "commonjs"

  Node.js is on it's way to add ES-Modules, but for now we'll have to stick with CommonJS.

• "target": "es2017"

  This tells TypeScript that it's okay to output JavaScript syntax with features from ES2017. In practice, this means that it will e.g. output async/await instead of embedding a polyfill (__awaiter).

• "lib": ["es2017"]

  This tells TypeScript that it's okay to use functions and properties introduced in ES2017 or earlier. In practice, this means that you can use e.g. Array.prototype.includes and String.prototype.padStart.

The full config would thus be:

{   "compilerOptions": {     "lib": ["es2017"],     "module": "commonjs",     "target": "es2017"   } } 

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If you are running Node.js 16 you can see my similar answer for Node.js 16 here

If you are running Node.js 14 you can see my similar answer for Node.js 14 here

If you are running Node.js 12 you can see my similar answer for Node.js 12 here

If you are running Node.js 10 you can see my similar answer for Node.js 10 here

Answer 2

I'm sure you've already found this but there is Microsoft's starter template here: https://github.com/Microsoft/TypeScript-Node-Starter

Whilst you are still on Node 8.x, keep your module set to commonjs, target can be es6.

compilerOptions.lib only defines what declarations the compiler uses for compile time checks, it does not affect the output of tsc. In other words, you can use whatever lib you want and not worry that your transpiled code will be any different (this is controlled entirely by compilerOptions.target).

Using es7 as a lib in your case will be fine and will give you type declarations for ES7 and under.

Array.includes is ES7 (ES2016) and therefore as you've discovered is not part of ES6. You could define your lib as; lib: ["es6", "ES2016.Array.Include"] to get around your issue.