Question

I wrote some JavaScript on Chrome and then tried to run it in IE8. The first thing I ran into was the lack of Array.map, Array.filter and all their useful cousins. To get around this, I added some of the shims found here.

This broke all my for ... in ... loops, like this:

>> c = [1];
{...}
>> for(i in c) { console.log(i);}
LOG: 1
LOG: indexOf
LOG: lastIndexOf
LOG: filter

I would want that to iterate over array entries only. Is there a way around this or do I need to go back to writing for(i=0;i<c.length;++i) loops?

Answer 1

You need to sanitize your loops, using hasOwnProperty the shim adds functionality to the array prototype and you end up looping over the added functions.

for(i in c){
    if(c.hasOwnProperty(i))
    {
        console.log(i);
    }
}

References:
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/hasOwnProperty

http://msdn.microsoft.com/en-us/library/328kyd6z(v=vs.94).aspx

Crockford on for .. in http://javascript.crockford.com/code.html search for “hasOwnProperty”