Making a function to wait an event before returning?

Question

function myFunction() {
    wait(); //what I put there?
    return;
}

myFunction(); 

//this is an event; when its triggered I want function to resume
onSomething = function() {
    myFunction.resume(); //what I put there?
}

Its just a local experience. Note that while(!resume) won't work because that would prevent the event onSomething to happen.

You can do that with [generators](https://developer.mozilla.org/en/JavaScript/Guide/Iterators_and_Generators), but that's not cross-browser. It will come with ECMAScript 6 though... — Šime Vidas, Nov 06 '11 at 13:51

score 5 · Answer 1 · answered Nov 06 '11 at 13:48

5

This is not possible.

Instead of waiting for the event, you want to put whatever you need to do when it happens into the onSomething function.

answered Nov 06 '11 at 13:48

Pekka

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This is indeed not possible on javascript and I realized it is not necessary too. – MaiaVictor Feb 11 '12 at 02:09
Here's a situation where such a feature is necessary: A function that captures `oncontextmenu` event, and needs to return true or false based on a mouse event. The browser contextmenu cannot be triggered programmatically. – automaton Mar 13 '15 at 10:12
@automaton how do you mean "based on a mouse event"? When would that mouse event take place if the user is currently in the context menu? – Pekka Mar 13 '15 at 16:16

score 4 · Answer 2 · answered Nov 06 '11 at 13:50

You have to switch your brains to thinking in events instead of the "traditional" programming flow. The way to do this is:

function myFunctionPart1() {
    doSomething();
}

function myFunctionPart2() {
    doSomethingElse();
}

myFunctionPart1();

onSomething = function() {
    myFunctionPart2();
}

Šime Vidas · Accepted Answer · 2011-11-06T14:15:30.393

So, with a generator it would look like so:

function test() {
    // first part of function
    yield;
    // second part of function
    yield;
}

var gen = test(); // creating a generator

gen.next(); // execute first part

button.onclick = function () {
    gen.next(); // execute second part on button click
};

Live demo: http://jsfiddle.net/MQ9PT/

This however doesn't work beyond Firefox. It will become part of the ECMAScript standard in the next edition...

Making a function to wait an event before returning?

3 Answers3

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