#js.next

[obscurejavascript]

JavaScript.next Implementations in Pure JS

Since I was on vacation last week, I have not had the usual time to come up with a post. Anyways, it turns out I have written current JavaScript implementations for quite a few of JS.next's features. The easiest way to try these is with Traceur. Here is a listing of posts with JS.next implementations in current JS and the Traceur examples:

Array Comprehension • Traceur Example

Computed Property Names • Traceur Example

Default Parameters • Traceur Example

Destructuring Assignment • Traceur Example

Object Initializer Shorthand • Traceur Example

Rest Parameters • Traceur Example

Spread • Traceur Example

Template Literals • Traceur Example

[obscurejavascript]

Spread VS Apply in JavaScript

This is the spread operation that will probably be available in future JavaScript versions:

function add(x, y) { return x + y; } var numbers = [4, 38]; console.log(add(...numbers));// 42

It turns an array into a list of formal parameters. But, unlike other Traceur features, it has an almost exact equivalent in current JS:

var numbers = [4, 38]; console.log(add.apply(null, numbers));// 42

You can read more about the apply operator here.

Github Location: https://github.com/Jacob-Friesen/obscurejs/blob/master/2014/spread.js

[obscurejavascript]

Computed Property Names In Literals

Many of my posts focus on syntactic advantages and in the future JavaScript is getting quite a few. Traceur can be used to test some of those features out. One of them is computed property values in literals. Usually, this would be required:

var x = 0; var obj = {}; obj[x] = 'hello'; console.log(obj[x]);// hello

But with a future proposal this is possible:

var x = 0; var obj = { [x] : 'hello' }; console.log(obj[0]);// hello

Which is arguably easier to read. Though, a similar syntax can be used in current JS if sent to a function:

var x = 0; var obj = toLiteral([ [x, 'hello'] ]); console.log(obj[x]);// hello

The implementation is quite simple:

var toLiteral = function(array) { var newLiteral = {} array.forEach(function(pair) { newLiteral[pair[0]] = pair[1]; }); return newLiteral; }

Github Location: https://github.com/Jacob-Friesen/obscurejs/blob/master/2014/computedProperties.js