Does node.js support the 'let' statement?

Question

Does node.js support a let statement something like what\'s described on MDN??

var x = 8,
    y = 12;

let ( x = 5, y = 10) {
    return x + y;
} //15


        

Answer 1

Yes, you can use let within node.js, however you have to run node using the optional --harmony flag. Try the following test.js:

"use strict"
var x = 8,
    y = 12;

{ let x = 5, y = 10; console.log(x + y); }

console.log(x + y);

And then run the file node --harmony test.js which results in:

15
20

I would not recommend using this in an important production application, but the functionality is available now.

Answer 2

I don’t think Node supports let, but you can do this:

var a = 5;

(function () {
  var a = 6;
  console.log(a); // => 6
})();

console.log(a); // => 5

Answer 3

This is an old question and the accepted answer is no longer correct.

let support was added in Node.js 4.x.

See here for the full version support matrix.

Answer 4

node --use_strict --harmony_scoping

Answer 5

You can use the Babel transpiler and use let as well as many other ES6/ES2015 features.

To use babel:

$ npm install --save-dev babel

Then in your package.json:

"scripts": {
  "start": "babel-node index.js"
}

Inside index.js:

let foo  = 'bar;

Then start the server:

$ npm start