var myFunc = function(){ var test = 0; setTimeout(function(){ test = 10; }, 5000); return test; } alert(myFunc());

How to get result 10 without using yield

  • one
    the answer is simple: no way, and yield in this case will not help in any way - Grundy
  • @Grundy plnkr.co/edit/96khBVXBTC3KvECmkhsZ?p=preview so - Serge Esmanovich
  • Uncaught ReferenceError: co is not defined - Grundy
  • @Grundy github.com/tj/co here - Serge Esmanovich
  • for nodejs - how strange it is to show an example in a browser that can only work in a node :) - Grundy

3 answers 3

And if you use async / await from ES7, you can do this:

 const myFunc = () => { return new Promise((resolve, reject) => { setTimeout(() => { resolve(10); }, 5000); }); }; (async function() { alert(await myFunc()); })();

And here is a working example on JSFiddle.

Yes, the definition of the myFunc function myFunc become more difficult. However, using async / await, we can write pseudo-sync code without explicitly using Promises and Generators . For example:

 let updatePost = async function(uid, pid, newBody) { let user = await loadUser(uid), post = await loadPost(pid), canEdit = await user.canEdit(post); if (!canEdit) { return false; } post.setBody(newBody); await post.save(); return true; };

But there is bad news. ES7 is not only not supported by browsers, but is not even accepted as standard. Although all the code above is well transported through Babel , browser native support is still far away.

  • Great, only this will be ES2017 to the standard by ES2017 , and then - if you're lucky. Now it is - just a superstructure above the language. - user207618
  • 2
    setTimeout(resolve, 5000, 10); :) - Qwertiy ♦
  • Now everything goes to the fact that sooner or later async/await will enter the standard. Painfully beautiful idea. And if so, then you need to prepare now. Moreover, this functionality is already in the Edge out of the box: kangax.imtqy.com/compat-table/esnext/#test-async_functions - Dmitriy Simushev
  • @Qwertiy, yes, you can. but visibility does not benefit from this - Dmitriy Simushev

If I correctly understood the condition of the problem.

  var myFunc = function(f) { var test = 0; setTimeout(() => { test = 10; f(test); }, 5000); } myFunc(alert);
  • yes thanks interesting implementation - Serge Esmanovich
  • one
    then f(10); is easier right away f(10); without unnecessary variables - Grundy

Maybe in the Promise wrap?

 var test = 0; (new Promise( function( resolve){ window.setTimeout( function(){ test = 10; resolve(test); }, 3000); })) .then( function(v){ alert(v); }) ;

The event variant may also be convenient. Since you have a question about asynchronous interaction, the pub-sub model is relevant.

In the example of an event we listen and throw out on the window object:

 var myFunc = function() { setTimeout(function() { window.dispatchEvent(new CustomEvent('ololo', { // в свойстве "detail" можно передать любые данные - // объект с кучей данных, или просто скалярное значение 'detail': { myTestData: 5, moreData: "trololo" } })); }, 2000); } window.addEventListener( 'ololo', function(e) { alert('' +e.detail.myTestData +' ' +e.detail.moreData); }, false ); myFunc();

  • Yes, and here the global variable is not needed, as in the next answer - Grundy
  • too, thanks for the example I'll take a note - Serge Esmanovich
  • can you just emit an event and listen to it? =) - Sergiks
  • @Sergiks if you add an emitter option to the answer, I think it will be useful - Serge Esmanovich
  • When using pub / sub, you have to think about the application in an asynchronous key (which is not always elementary). This is one of the reasons why a bunch of nested callback functions were used before, and now Promises . Well, error handling when using pub / sub is not very fun. - Dmitriy Simushev