JavaScript jQuery间隔中的全局变量

Question

I have got code like this

var challegneListener;

$(document).ready(function(){
    var challegneListener = setInterval("challengeListenerBot()",5000);
});

function challengeListenerBot(){
    clearInterval(challegneListener);
}

And the problem is that the interval does not stop, becouse function called challengeListenerBot does not see challegneListener variable as number of interval. I must use jQuery to start interval when the document is ready.

Answer 1

Change this:

$(document).ready(function(){
    var challegneListener = setInterval("challengeListenerBot()",5000);
});

To this:

$(document).ready(function(){
    challegneListener = setInterval("challengeListenerBot()",5000);
});

The problem is you're declaring inside your anonymous function, called when the DOM is ready, a new challengneListener variable. It hides the global variable, and only saves the setInterval ID to the local variable, which is garbage collected when its enclosing function has finished executing.

Answer 2

$(document).ready(function(){
var challegneListener = setInterval("challengeListenerBot()",5000); 
});

Using var inside this function creates a new variable that is scoped to this function, meaning that the challegneListener variable that is defined globally remains undefined hence the interval not being cleared. Remove the var to fix this code.

Answer 3

You hide the global variable, remove the var :

$(document).ready(function(){
    challegneListener = setInterval("challengeListenerBot()",5000); 
    // removed the var keyword, because it hides the global var.
});

Another thing, your code uses eval , change it to this:

challegneListener = setInterval(challengeListenerBot, 5000);