有一个 indexOf 方法，所有数组(Internet Explorer 8 及以下版本除外)都将返回数组中元素的索引，如果不是，则返回 -1在数组中:

There is an indexOf method that all arrays have (except Internet Explorer 8 and below) that will return the index of an element in the array, or -1 if it's not in the array:

if (yourArray.indexOf("someString") > -1) {
    //In the array!
} else {
    //Not in the array
}

如果你需要支持旧的IE浏览器，你可以使用MDN 文章.

If you need to support old IE browsers, you can polyfill this method using the code in the MDN article.