ecmascript-harmony

I am trying to do the obvious thing with WeakMaps: I want to create a weak reference. In particular, I want to have a list of event-listeners without that list influencing the life of the listener. So I was very excited to find WeakMaps, until I saw they were only built to satisfy one (fairly rare) use-case, extending objects that were otherwise sealed. I can't think when I ever wanted to do that, but I need lists of listeners all the time. Is this possible to use WeakMaps in some clever way I haven't thought of to do this? Bergi No, it is impossible to use WeakMaps to create a weak reference.

Is it possible to enable EcmaScript 6 Harmony Proxies in nodejs? If so, what are the pros and cons? And is there any documentation on how to use them? Thanks ! Invoking node with node --harmony-proxies should do the trick. Pros: proxies are a very powerful feature when you really need them. Cons: proxies are a much too powerful feature when you don't need them (which should be most of the time). Also, the implementation should still be regarded experimental. As for documentation, all there really is atm is the Harmony wiki, in particular this page, which reflects the current implementation of

Does anyone know how to write an immediate function using ES6 arrow syntax? Here's the ES3/5 way of doing it: (function () { //... }()); I've tried the following but get an unexpected token error on the last line. (() => { //... }()); You can test this here: http://www.es6fiddle.net/hsb8bgu4/ From the Arrow functions examples , (() => "foobar")() // returns "foobar" So, the function invocation operator should be outside. (() => { //... })(); Sample: http://www.es6fiddle.net/hsb8s1sj/ Here is my demo codes! Always remember that function_name + () === function_caller /* ES5 */ // normal function

This question already has an answer here: Is there a mechanism to loop x times in ES6 (ECMAScript 6) without mutable variables? 15 answers What is the best way to do the below in more functional way (with ES6/ES7) let cols = []; for (let i =0; i <= 7; i++) { cols.push(i * i); } return cols; I tried like, return [ ...7 ].map(i => { return i * i; }); but that translated to [].concat(7).map(function (n) { return n * n; }); which is not what I expected. EDIT: @pavlo. Indeed, that was a mistake. I was using JSX, and for example, I want 7 divs, (untested) let cols = []; for (let i =0; i <= 7; i++) {

I came up with this simple experiment after reading the documentation on generators from MDN : var nodes = { type: 'root', value: [ { type: 'char', value: 'a' }, { type: 'char', value: 'b' }, { type: 'char', value: 'c' }, ], }; function* recursiveGenerator(node) { if (node.type === 'root') { node.value.forEach(function (subnode) { for (var suffix of recursiveGenerator(subnode)) { yield suffix; } }); } else { yield node.value; } } for (generated of recursiveGenerator(nodes)) { console.log(generated); } Running it on node.js v0.11.9 with the --harmony flag set produces the following error: alix

Given the provided (very simple) generator, is it possible to return the generator back to its original state to use again? var generator = function*() { yield 1; yield 2; yield 3; }; var iterable = generator(); for (let x of iterable) { console.log(x); } // At this point, iterable is consumed. // Is there a method for moving iterable back // to the start point by only without re-calling generator(), // (or possibly by re-calling generator(), only by using prototype // or constructor methods available within the iterable object) // so the following code would work again? for (let x of iterable

I have a problem where I'm generating many values and need to make sure I only work with unique ones. Since I'm using node js, with the --harmony flag, and have access to harmony collections, I decided that a Set may be an option. What I'm looking for is something similar to the following example: 'use strict'; function Piece(x,y){ this.x = x this.y = y } function Board(width,height,pieces){ this.width = width this.height = height this.pieces = pieces } function generatePieces(){ return [ new Piece(0,0), new Piece(1,1) ] } //boardA and boardB are two different but equivalent boards var boardA