esnext 是一个 JavaScript 库，可以将 ES6 草案规范语法转成今天的 JavaScript 语法。
例如：
/*
On the left is code written with new JavaScript features,
and on the right is the console output, plus the same code
re-written so it can run in today's browsers.
Edits made to the code on the left will re-generate and
re-run the code on the right. Try it out!
*/
// Classes
class Person {
constructor(firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
get name() {
// Template strings
return `${this.firstName} ${this.lastName}`;
}
toString() {
return this.name;
}
}
console.log(
'Full name is:',
new Person('Michael', 'Bluth')
);
// Arrow functions
console.log([1, 2, 3].map(x => x * x));
// Rest params
function join(delim, ...items) {
return items.join(delim);
}
// Spread args
console.log(join('-', ...[415, 555, 1212]));
将被转换成：
/*
On the left is code written with new JavaScript features,
and on the right is the console output, plus the same code
re-written so it can run in today's browsers.
Edits made to the code on the left will re-generate and
re-run the code on the right. Try it out!
*/
// Classes
var $__Array$prototype$slice = Array.prototype.slice;
var $__Object$defineProperties = Object.defineProperties;
var Person = function() {
"use strict";
function Person(firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
$__Object$defineProperties(Person.prototype, {
name: {
get: function() {
// Template strings
return "" + this.firstName + " " + this.lastName + "";
},
enumerable: true,
configurable: true
},
toString: {
value: function() {
return this.name;
},
enumerable: false,
writable: true
}
});
$__Object$defineProperties(Person, {});
return Person;
}();
console.log(
'Full name is:',
new Person('Michael', 'Bluth')
);
// Arrow functions
console.log([1, 2, 3].map(function(x) {
return x * x;
}));
// Rest params
function join(delim) {
var $__arguments = arguments;
var items = [].slice.call($__arguments, 1);
return items.join(delim);
}
// Spread args
console.log(join.apply(null, ['-'].concat($__Array$prototype$slice.call([415, 555, 1212]))));
使用方法：
var transpiler = require('es6-module-transpiler');
var Container = transpiler.Container;
var FileResolver = transpiler.FileResolver;
var BundleFormatter = transpiler.formatters.bundle;
var container = new Container({
resolvers: [new FileResolver(['lib/'])],
formatter: new BundleFormatter()
});
container.getModule('index');
container.write('out/mylib.js');