Package Exports

esnext

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (esnext) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

esnext

Bring your JavaScript into the future.

Installation

$ npm install -g esnext

Usage

After installing, run esnext -h for comprehensive usage instructions.

Features

Functions

Translate some regular functions to arrow functions:

list.map(function(item) { return item.name; });

// ↑ becomes ↓

list.map(item => item.name);

Declarations

Convert var declarations to let or const as appropriate:

var arr = [];
for (var i = 0; i < 5; i++) {
  arr.push(i);
}

// ↑ becomes ↓

const arr = [];
for (let i = 0; i < 5; i++) {
  arr.push(i);
}

Objects

Use shorthand syntax for various object constructs:

let person = {
  first: first,
  last: last,
  
  fullName: function() {
    return `${first} ${last}`;
  }
};

// ↑ becomes ↓

let person = {
  first,
  last,
  
  fullName() {
    return `${first} ${last}`;
  }
};

Strings

Convert string concatenation to string or template literals:

let name = 'Brian' + ' ' + 'Donovan';
let greeting = 'Hello, ' + name;

// ↑ becomes ↓

let name = 'Brian Donovan';
let greeting = `Hello, ${name}`;

Destructuring

Convert assignments and declarations to use object destructuring syntax:

let a = obj.a, b = obj.b;
a = obj2.a, b = obj2.b;

// ↑ becomes ↓

let { a, b } = obj;
({ a, b } = obj2);

Modules

Translate CommonJS modules into ES6 modules:

var readFile = require('fs').readFile;
const MagicString = require('magic-string');
let { ok, strictEqual: eq } = require('assert');

exports.doSomething = function() {
  ok(1);
};

// ↑ becomes ↓

import { readFile } from 'fs';
import MagicString from 'magic-string';
import { ok, strictEqual as eq } from 'assert';

export function doSomething() {
  ok(1);
}

Options

{
  'declarations.block-scope': {
    /**
     * Set this to `true` to only turn `var` into `let`, never `const`.
     */
    disableConst: boolean
  },
  /**
   * Pass a custom function to parse the code as desired. Most likely you'll
   * want to use `babel-eslint` to parse any valid babel code. To set this
   * option in code, do something like this:
   *
   *   import { parse } from 'babel-eslint';
   *   convert(code, { parse: parse });
   *
   * To set this option from the command-line interface, make sure your custom
   * parser is installed, then use it like so:
   *
   *   $ esnext -I index.js --parser babel-eslint
   */
  parse: (source: string) => AST
}