时间：2021-03-06 10:11:08 | 栏目：JavaScript代码 | 点击：次
实例如下：
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;
};