var string = "foo",
    substring = "oo";
console.log(string.indexOf(substring) !== -1);

如果不存在,则string.indexOf(substring)函数的返回值为-1;

 

更加现代的方法--

(ES6) includes

var string = "foo",
    substring = "oo";
string.includes(substring);

search

var string = "foo",
    expr= "/oo/";
string.search(expr);

根据性能测试,indexOf是最快的方法