Implementation of JavaScript array length property

Took 12 minutes 48 seconds to implement JavaScript array length property. The maximum length of the array can only be 10000. Here is the code snippet.

Function:

arr = ['1', '2', '3', '4'];

count = 0;

function length(arr) {

for (var i = 0; i < 10000; i++) {

if(arr[i] != undefined) {

count++;

}

}

return count;

}

document.write(length(arr));

Result:

4