Function return a list of values that could only be get asynchronously

Question

I'd like to write this function:

function getResults(nums){
    var results = [];
    for(var i = 0, len = nums.length; i < len; i++){
        var num = nums[i];
        ajaxGet("http://xxx.com/" + num, function(data){
            results.push(data);
        });
    }
    return results;
}    
var results = getResults([12, 22, 34]);

as you can see, because ajaxGet is asynchronous, this won't work. How could I do this properly?

The only problem I see in your code is: results.push[data]; -> results.push(data); — Itay Moav -Malimovka, Jan 22 '12 at 05:12
@ItayMoav Oh that's a typo, thanks. do you think the code above could get the correct result? — wong2, Jan 22 '12 at 05:14

score 4 · Answer 1 · answered Jan 22 '12 at 05:21

4

You could also tell Ajax to run synchronously

$.ajax({async: false});
var results = getResults();
$.ajax({async: true});

answered Jan 22 '12 at 05:21

Jason

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1

https://stackoverflow.com/questions/748175/asynchronous-vs-synchronous-execution-what-does-it-really-mean – Jason Sep 21 '18 at 17:40

SLaks · Accepted Answer · 2012-01-22T05:18:41.493

You need to return the array using a callback, and call the callback when you receive the last response. (note that responses will not be received in order)

function getResults(nums, callback) {
    var results = [];
    for(var i = 0, len = nums.length; i < len; i++){
        var num = nums[i];
        ajaxGet("http://xxx.com/" + num, function(data){
            results.push(data);
            if (results.length === nums.length)
                callback(results);
        });
    }
}

score 0 · Answer 3 · edited May 23 '17 at 12:09

If you're using jQuery you can set the async flag to false:

function getResults(nums){
    var results = [];
    for(var i = 0, len = nums.length; i < len; i++){
        var num = nums[i];
        jQuery.ajax({
            url: "http://xxx.com/" + num}, 
            async: flase,
            success: function(data){
                results.push(data);
            }
        });
    }
    return results;
}    
var results = getResults([12, 22, 34]);

But if you're doing it this way then your approach is wrong. Go with SLaks answer instead.

jQuery.ajax() API page

score 0 · Answer 4 · answered Jan 22 '12 at 05:22

var allresults;

function getResults(nums){
    var results = [];
    for(var i = 0, len = nums.length; i < len; i++){
        var num = nums[i];
        ajaxGet("http://xxx.com/" + num, function(data){
            results.push(data);
            if(results.length == nums.length){
                 resume(results);
            }
        });
    }

}

getResults([12, 22, 34]);

function resume(results){
   allresults =  results;
   ....
   ....
}

Like others said, use if you are not using jQuery

Function return a list of values that could only be get asynchronously

4 Answers4