JS For Loop Stopping Early after Calling Function

Question

I have a Javascript Array that holds the contents of a page. In order to draw all the objects in the right places when the page loads I loop over the array and pull out the elements. This worked very well until I allowed the objects to have children within them.

The current array structure is 0-> {elements=[] frame={I keep the frame attributes here with key value pairs}}, 1-> {elements=[] frame={}}

However, I just started adding sub-elements to the elements array in each object. So now I have to loop through/draw each element, check to see if there are any children and if so then I have to draw them too.

The problem I'm having is that after I loop through the first 0 object and it's children the for loop stops running. Is it because I'm calling the same function multiple times? I've done that before so I don't think that's what is happening.

this.run_loop = function (spawn, dom) {
    console.log(spawn)
    alert(spawn.length)
    for (i = 0; i < spawn.length; i++) {
        console.log(spawn[i])
        //alert("i one")    
        var newdom = dom + "_" + i;
        this.synthesize_elements(spawn[i], dom, newdom)
        if (spawn[i].hasOwnProperty('elements')) {
            //alert("FOUND")
            var newarray = spawn[i]['elements'];
            if (newarray.length > 0) {
                this.run_loop(newarray, newdom)
            }
        }
    }
}

No. It just doesn't run. If I comment out this.run_loop(newarray, newdom) it runs through the top two arrays perfectly. It's only when I loop it through the child arrays that I have a problem — centreee
– centreee, Commented Dec 5, 2013 at 19:10
Could you create a minimal complete example that demonstrates your problem? I can't test your code because you are referencing functions that aren't defined in your example. — Peter Olson
– Peter Olson, Commented Dec 5, 2013 at 19:16
Agree with @PeterOlson, it's probably a bug in other code not shown here; for example the synthesize_elements call probably doesn't do what you think it does. — Chris Moschini
– Chris Moschini, Commented Dec 5, 2013 at 19:31

bryan60 · Accepted Answer · 2015-09-16 22:40:23Z

3

This is a little old but I encountered a similar issue and found my way here, but I figured it out and thought I'd post the solution if anyone else came across this. The issue in my case (and it looks like in your case as well though I can't be sure) was in the declaration of the for loop:

for (i = 0; i < spawn.length; i++)

You're not declaring that i is a new var. so if anything inside the

this.run_loop(newarray, newdom)

function also manipulates a counter variable called i that isn't declared a new var, it will also change the one in your outer scope, and kick you out of the loop if it goes over the length of spawn

just always declare:

for (var i; i< spawn.length; i++)

in your loops or make sure your counters are unique.

answered Sep 16, 2015 at 22:40

bryan60

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