JavaScript loop waiting some function return then do next loop

Question

I use the code below to wait, then do next loop:

function loop()
{
    setTimeout(function()
    {
        process_number(a[i]);
        i++;
        if (i < a.length)
            loop();
        else
        {
            alert("done!");
        }
    }, 5000);
}

I want to change to like jQuery $.get callback function executed when get complete .

$.get("test.cgi", { name: "John", time: "2pm" },
  function(data){
  alert("Data Loaded: " + data);
});

function loop()
{
    //where process_number executed complete, do next loop
    //process_number(a[i]);
    i++;
    if (i < a.length)
        loop();
    else
    {
        alert("done!");
    }
}

the function process_number Execution time is uncertain.

what happens at process_number(a[i]);? (and if it is irrelevant, you shouldn't have included it) and what is the first value of i? — ajax333221
– ajax333221, Commented Apr 17, 2012 at 15:54
process_number(a[i]) is the process data function, it is very Important. i first value is 0. @ajax333221 — flyingnn
– flyingnn, Commented Apr 17, 2012 at 16:04
I meant like irrelevant to the question, (i know it is important to you). In this site you are supposed to shrink down your code to the less code possible to reproduce the problem. But well, not everyone spend 1 hour reading faq before posting — ajax333221
– ajax333221, Commented Apr 17, 2012 at 16:10

Tuan · Accepted Answer · 2012-04-17 15:51:52Z

1

You can add a callback parameter to your loop() function and execute it when desired:

function loop(callback)
{
    //where process_number executed complete, do next loop
    //process_number(a[i]);

    if (callback) {
        callback();
    }
}

loop(function () {
    alert("continuing...");
});

answered Apr 17, 2012 at 15:51

Tuan

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Comments

Baxter · Accepted Answer · 2012-04-17 15:53:45Z

1

Very basically you can just pass a function name as a parameter and then call it though the argument name, this works just as well with anonymous functions:

function foo(x,callback)
{
    callback(x);
}

foo("hello",alert)
foo("hello",function(x){alert(x);});

answered Apr 17, 2012 at 15:53

Baxter

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