IE Javascript Array.indexOf() error

if (!Array.prototype.indexOf) {
Array.prototype.indexOf = function(elt, from) {
var len = this.length >>> 0;
var from = Number(arguments[1]) || 0;
from = (from < 0) ? Math.ceil(from) : Math.floor(from);
if (from < 0) from += len;
for (; from < len; from++) {
if (from in this && this[from] === elt) return from;
}
return - 1;
};
}

References :
[JS] IE 的 JS 陣列不可使用 indexOf() - 楓葉筆記本- 點部落