Function call within a for loop terminates the loop?

Question

I am experiencing a funny issue with JavaScript. I have a feeling this could have something to do with Closures, which, I admit, I am not really comfortable with.

Problem It seems that calling a function from within results in a premature termination of the loop. I tried running the same loop without the function call and console.log() outputs the counter accurately suggesting the function call is breaking the loop.

Could someone suggest a possible fix? I have the code pasted here:

AbstractModel.prototype.deactivateContext   = function(context){

  for(i=0;i<this.asset.length;i++){
      if(this.asset[i].context == context){
        this.asset[i].deactivate();
        console.log(i);
        this.notify(this.asset[i],"REFRESHASSETS");
      }
  }
}

Where did you call this method? (Did you call the method?) This is just a method definition; it won't actually run the body. — user2357112
– user2357112, Commented May 2, 2014 at 13:35
Which particular function call seems to be the problem? There are 3 in that loop. — user2357112
– user2357112, Commented May 2, 2014 at 13:37
AbstractModel will have a method called deactivateContext. Looks like you have Assets object with method called deactivate. If you show us the invocations and more code, we will be able to comment better — closure
– closure, Commented May 2, 2014 at 13:38
Oh, I found it. i is not declared. i is coming from global context. — closure
– closure, Commented May 2, 2014 at 13:39
You forgot to declare "i" with var. If the other function also uses "i" to control a loop, then you'll have problems. — Pointy
– Pointy, Commented May 2, 2014 at 13:39

epascarello · Accepted Answer · 2014-05-02 13:40:11Z

5

var is not optional

You proabbly have a global i in the other method. Declare your variables to the correct scope.

for (var i=0; i<this.asset.length; i++) {
     ^^^

answered May 2, 2014 at 13:40

epascarello

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2 Comments

user77838 Over a year ago

Yeah, the issue is probably a side effect altering either "i" or this.asset.length

captainspi Over a year ago

I am using 'i' in the other function (notify) as well without explicitly declaring it there which would explain why the loop ends early. Cheers!

closure · Accepted Answer · 2014-05-02 13:42:02Z

3

Please declare i in the following function, like

AbstractModel.prototype.deactivateContext   = function(context){

  for(var i=0;i<this.asset.length;i++){
      if(this.asset[i].context == context){
        this.asset[i].deactivate();
        console.log(i);
        this.notify(this.asset[i],"REFRESHASSETS");
      }
  }
}

Looks like i is getting modified to a higher number in the notify function, when it returns from notify the for check is exiting.

answered May 2, 2014 at 13:42

closure

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Comments

milagvoniduak · Accepted Answer · 2014-05-02 13:40:09Z

1

Have you tried wrapping the call to the notify function in try catch. If you are saying that when you remove the call, output of counter prints as expected then the only explanation would be that your function is throwing an exception. Try this:

 for(i=0;i<this.asset.length;i++){
      if(this.asset[i].context == context){
        this.asset[i].deactivate();
        console.log(i);
        try {
          this.notify(this.asset[i],"REFRESHASSETS");
        } catch(e) {
           alert(e);
           console.log(e);
        }
      }
  }

answered May 2, 2014 at 13:40

milagvoniduak

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2 Comments

captainspi Over a year ago

+1, that's a really smart debugging tip but the issue was resolved by declaring the counter explicitly. I am using 'i' in the other functino (notify) as well without explicitly declaring it which would explain why the loop ends early. Thanks!

milagvoniduak Over a year ago

oh cool, sorry did notice that you are not declaring var explicitly.

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