JavaScript Array对象扩展indexOf()方法_javascript技巧

背景：JavaScript中Array对象的标准方法中，没有indexOf()方法，可通过下面的代码扩展。

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