how to sync between two functions

Question

I have two functions that I want to call to third function when the other functions( one and two ) will be finished. I need that the first function and the second function will be called Asynchronous. for example

  var func1 = function( do something..... return arr )
  var func2 = function ( do something ..... return arr2 )

   if ( arr.length > 0  && arr2.length > 0 )
       var func3 = function( do something )

my qeustions:

what is the best way to do it ?
How I call to function in Asynchronous way ?

So you want to call the third function after you execute the first and the second? — Vlad Balmos, Aug 23 '12 at 13:35
yes but I want that the first function and the second function will be called in Asynchronous way — user1365697, Aug 23 '12 at 13:39
I mean that I call to func1 and I don't know when the function will be finsihed , also it is possible that the func2 will finish before the first function.Only when I have the data of arr and arr2 I need to call to func3 — user1365697, Aug 23 '12 at 13:41
I don't want to call synchronous way meaning to call func1 get result and then to call to func2 and get result.I don't know when the function will be finished — user1365697, Aug 23 '12 at 13:43
If you are working on a NodeJS project, I would suggest you look into [**Iced CoffeeScript**](http://maxtaco.github.com/coffee-script/). — Gautham Badhrinathan, Aug 23 '12 at 14:02

score 5 · Accepted Answer · edited May 23 '17 at 11:58

If you have jQuery, you could use their Deferred objects:

var func1 = function () {
    var dfd = $.Deferred();

    setTimeout(function () {
        // do your processing
        dfd.resolve(arr1);
    }, 0);

    return dfd.promise();
};
var func2 = function () {
    var dfd = $.Deferred();

    setTimeout(function () {
        // do your processing
        dfd.resolve(arr2);
    }, 0);

    return dfd.promise();
};

$.when(func1(), func2()).then(function (arr1, arr2) {
    if ( arr.length > 0  && arr2.length > 0 ) {
        func3();
    }
});

Related questions:

Yup, `Deferred` & `Promise` is pretty neat! – Gautham Badhrinathan Aug 23 '12 at 13:58 — Gautham Badhrinathan, Aug 23 '12 at 13:58

Vlad Balmos · Answer 2 · 2012-08-23T13:48:05.217

0

var arr1 = [], arr2 = [];

function arraysAreReady() {
     if(arr1.length && arr2.length) {
         func3();
     }
}

var func1 = function() {
    var localArray = [];
    /// create the local array
    arr1 = localArray;
    arraysAreReady();
}

var func2 = function() {
    var localArray = [];
    /// create the local array
    arr2 = localArray;
    arraysAreReady();
}

func1(); funct2();

when func1 has created the first array it wil assign it to the global variable arr1 and call arraysAreReady() function. when func2 has created the second array it will asign it to the global variable arr2 and call arraysAreReady().

the arraysAreReady() function checks on each call if the 2 global arrays are not empty. Is they are not the it will call the third function (func3)

edited Aug 23 '12 at 13:48

answered Aug 23 '12 at 13:38

Vlad Balmos

3,372
19
34

but the problem that I dont know when the func1 and func2 will be finished , I need that those function will be called Asynchronous so I don't know when arr and arr2 have a data – user1365697 Aug 23 '12 at 13:40
I can use the func3 only when both function will finished – user1365697 Aug 23 '12 at 13:44

score 0 · Answer 3 · answered Aug 23 '12 at 13:44

Pass the func3 function as a callback and check inside your callback if both arrays are filled.

var func1 = function(callback) ( do something; callback();..... return arr );
var func2 = function(callback) ( do something; callback(); ..... return arr2 );
var func3 = function() {
    if(arr != undefined && arr2 != undefined){  
        //do stuff
    }
};

func1(func3); 
func2(func3);

score 0 · Answer 4 · answered Aug 23 '12 at 14:07

If your program logic is suitable, you can imitate asynchronous behavior in javascript by doing partial processing and using setTimeout() function as follows:

var result1 = []
var result1Ready = false;
var result2 = []
var result2Ready = false;

func1 = function(list, start, end) {

    if(start>=end) {
        result1Ready = true;
    }
    else {
        partialEnd = start+10>end ? end : start+10;
        for(i=start;i<partialEnd;i++) {
            //process 10 items
            //append results to array result1
        }
        //schedule second partial process
        setTimeout(function () { func1(list, partialEnd, end); }, 50);
    }
};

func2 = function(list, start, end) {
    //similar to func1...
};

waitResults = function() {

    if(result1Ready && result2Ready) {
        func3();
    }
    else {
        setTimeout(function () { waitResults(); }, 50);
    }
};

setTimeout(function () { func1(someList, 0, listLength); }, 5);
setTimeout(function () { func2(someOtherList, 0, otherListLength); }, 5);
setTimeout(function () { waitResults(); }, 10);

how to sync between two functions

4 Answers4