ecmascript-harmony

I'm trying to figure out how to get the value of a promise via yield , possibly with "co": function *(){ var someVar = yield functionThatReturnsAPromise(); } The called function is not a generator, just a normal function. With the above, someVar == Promise , but I want the resolved value. Does co or some other library have a way of doing this? Yes, co can do that. You'll have to wrap parent function inside co call: co(function *(){ var someVar = yield functionThatReturnsAPromise(); })() someVar inside will become resolved value. If promise gets rejected, error can be cought with basic try {}

I try to create a class on my node.js / express app. It works in basic js / prototype mode such as : function MyClass() { /* constructor code */ }; MyClass.prototype.myMethod = function() { /* method code */ }; module.exports = MyClass; But I want to do use the class, constructor, extends, ... keywords. I've try that : class MyClass { constructor() { /* constructor code */ } myMethod() { /* method code */ } } But it doesn't work, the error is : class MyClass { ^^^^^ SyntaxError: Unexpected reserved word My command line to launch the app with all harmony options : node `node --v8-options | grep

Now that node.js supports ECMAScript Harmony generators we can write monadic code succinctly ala do blocks in Haskell: function monad(unit, bind) { return function (f) { return function () { var g = f.apply(this, arguments); return typeOf(g) === "Generator" ? send() : unit(g); function send(value) { var result = g.next(value); if (result.done) return unit(result.value); else return bind(result.value, send); } }; }; } function typeOf(value) { return Object.prototype.toString.call(value).slice(8, -1); } In the code above monad is a function which can be used to create deterministic monads like:

Suppose I have a class in one big file like this: export default class { constructor () {} methodA () {} methodB () {} methodC () {} } And I want to break up the class definition so that methodA , methodB , and methodC are each defined in their own separate files. Is this possible? You should be able to, as class is supposed to just be syntax sugar for the usual prototype workflow: import methodOne from 'methodOne' import methodTwo from 'methodTwo' class MyClass { constructor() { } } Object.assign(MyClass.prototype, {methodOne, methodTwo}) export default MyClass @elclanrs gave a correct answer

I'm trying to use the new (ES6) Map objects in order to represent a map between properties and a value. I have objects in a form similar to: {key1:value1_1,key2:value2_1},..... {key1:value1_N,key2:value2_N} I want to group them based on both their key1 and key2 value. For example, I want to be able to group the following by x and y : [{x:3,y:5,z:3},{x:3,y:4,z:4},{x:3,y:4,z:7},{x:3,y:1,z:1},{x:3,y:5,z:4}] And obtain a Map containing: {x:3,y:5} ==> {x:3,y:5,z:3},{x:3,y:5,z:4} {x:3,y:4} ==> {x:3,y:4,z:4},{x:3,y:4,z:7} {x:3,y:1} ==> {x:3,y:1,z:1} In Python, I'd use tuples as dictionary keys. ES6

After reading Peter's article on JavaScript I noticed Brendan Eich stated that one the goals for Harmony is to be a better target for to-JavaScript compilers. There are currently two popular compilers with some vague ES:Harmony compliance: Traceur CoffeeScript Although CoffeeScript has some compliance it's not designed to be an ES:Harmony compiler so it's not useful to this end. Tracuer seems to be sticking more rigorously to the ES:Harmony specification but I don't know whether it intends to become a full ES:Harmony compiler. Since the aim is to to compile ES6 down to ES3 it would also need

export default var foo = {...} It's AssignmentExpression and valid es6 syntax? JSHint says it Expected an identifier and instead saw 'var'. On last spec I not found any relation with VariableStatement and AssignmentExpression. var foo = {...} is not an AssignmentExpression . AssignmentExpression is almost the top level non-terminal symbol that represents all expression , i.e. basically every expression is an AssignmentExpression . var only appears in a variable declaration or a for loop, so drop the var . 来源： https://stackoverflow.com/questions/24925628/es6-export-default-assignmentexpression

Look at this jQuery code: var promise = new Deferred(), some; some = function(promise) { // do cool things promise.resolve(); }; promise.then(/* callback cool things */); // init everything some(promise); I am not sure about architecture correctness of such approach, but I used it for long time and it is convenient for me. In native JavaScript I can not use such approach. Constructor new Promise() requires a callback parameter, so I can not pass instance of Promise as a parameter. So my question is: how can I predefine JavaScript native promise, pass it as a parameter to function and the