strange for-in loop output

[jonavanmona]

Hi, i found this strange thing in firefox.

if i alert the output of a simple 'for in' loop, it returns first the right value and then:

function forEach(){ 
[native code]

why is it doing this? it gives an error and its not in the array at all..?

[gits]

hi ...

with javascript 1.6 (gecko-engine 1.8b2 or greater) the Array will have a native forEach()-method ... to which you may refer here and there you will see how you could implement it in a enviroment where you don't have that native method. using a custom implementation for the array results in your observed behaviour ... a for-in loop will loop over the 'array'-keys and ALL methods that are 'custom' extensions for the native array-object ... so you just have to use the 'determined' for loop - have a look at the following example:

var a  = [1, 3, 4];
 
var cb = function(val) {
    alert(val);
};
 
// newer FF will alert the array values here
if (typeof a.forEach != 'undefined') {
    a.forEach(cb);
}
 
// we extend the native array now
Array.prototype.test = function() {
}
 
// you will get 0...2 AND test alerted
for (var i in a) {
    alert(i);
}
 
// using the 'determined' loop behaves 'correct' regarding
// the array-values
for (var i = 0; i < a.length; i++) {
    alert(i);
}
 

kind regards