Javascript call only once a child function with setInterval()

Question

I want to call myfun1 only once with setInterval. I want to avoid using a global variable. Read this but it does not work (just calls the function every 2000 ms). Naturally I need to call main() every 2000 ms.

(function($){         
    setinterval(main,2000);  

     function main (){            
        if(/*condition*/) return;

        function callItOnce(fn) {
            var called = false;
            return function() {
                if (!called) {
                    called = true;
                    return fn();
                }
                return;
            }
        }

        myfun1 = callITOnce(myfun1);
        myfun1();

        function myfun1(){/*code*/};
        function myfun2(){/*code*/};
        function myfun3(){/*code*/};
})(jquery);

You defined the function `callItOnce` and then used the function `callOnce`. — zzzzBov, Aug 02 '12 at 19:45
If you only want it invoked once, why are you using `setInterval`? — , Aug 02 '12 at 19:45
Because I'm checking other stuff dynamically, need it that way. — jacktrades, Aug 02 '12 at 19:47
Does that particular part of the function need to be inside of setinterval since you are only calling it once? — Kevin B, Aug 02 '12 at 19:49

adeneo · Accepted Answer · 2012-08-02T19:50:41.173

5

Use a flag :

(function($){ 
    var timer = setInterval(main,2000), ran=true;

    function main() {
        if(/*condition*/) return;

        if (ran) { //runs when ran=true, which is only the first time
            myfun1();
            ran = false;  //since it's set to false here
        }

        function myfun1(){/*code*/};
        function myfun2(){/*code*/};
        function myfun3(){/*code*/};

})(jquery);

edited Aug 02 '12 at 19:50

answered Aug 02 '12 at 19:45

adeneo

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it looks like OP is trying to perform more than one function within the `main` function. I had the same initial knee-jerk reaction, but I don't think that this is necessarily the correct answer. – zzzzBov Aug 02 '12 at 19:47
@adeno: OP wants to execute everything else inside `main` all the time, except for the call to `myfun1` which OP only wants to execute once. – Nope Aug 02 '12 at 19:49
Correct! Thanks for understanding – jacktrades Aug 02 '12 at 19:51
1

+1. I just fixed the syntax errors in the sample code so it can execute. See working DEMO here: http://jsfiddle.net/FranWahl/aWWay/ – Nope Aug 02 '12 at 19:56

score 0 · Answer 2 · answered Aug 02 '12 at 19:52

The callItOnce function you wrote should work. You just need to declare the function outside the setInterval call. Otherwise it gets redefined each time.

(function () {

function myfun1(){/*code*/};
function myfun2(){/*code*/};
function myfun3(){/*code*/};

function callItOnce(fn) {
    var called = false;
    return function() {
        if (!called) {
            called = true;
            return fn();
        }
        return;
    }
}

myfun1 = callItOnce(myfun1);

function main() {
    if(/*condition*/) return;
    myfun1();
}

setInterval(main, 2000);

}());

score 0 · Answer 3 · answered Aug 02 '12 at 21:09

One easy way to work around this is to use a variable on the function itself.

function myFunc1(){

if(arguments.callee.done){return;}


arguments.callee.done = true;    

}

This way the "done" variable on the method myFunc1 would make sure the method is executed only once.

score -1 · Answer 4 · answered Aug 02 '12 at 19:47

-1

setInterval returns a value that you can pass to clearInterval to stop the callback from being called.

var i = 0;
var timeout_id = setTimeout(function(){
    console.log(i);
    if(i >= 5){ clearTimeout(timeout_id) }
    i++;
})

answered Aug 02 '12 at 19:47

hugomg

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That's another option, but I want to call only myFun1() once, others with the interval... – jacktrades Aug 02 '12 at 19:49
1

@missingno: This will stop the callback altogether. OP seems to want the callback to continue but not execute `func1` inside it more than once. – Nope Aug 02 '12 at 19:51

Javascript call only once a child function with setInterval()

4 Answers4