javascript实现快速排序

'use strict';
/* jshint node: true */

const len = 100;
const ary = new Array(len).fill(0).map(() => Math.floor(Math.random() * len));

let ret = (function fastsort(ary) {
	if (ary.length <= 1) return ary;

	let k = Math.floor(Math.random() * ary.length);
	let l_ary = ary.filter((item, index) => (index != k) && (item < ary[k]));
	let r_ary = ary.filter((item, index) => (index != k) && (item >= ary[k]));

	return fastsort(l_ary).concat(ary[k]).concat(fastsort(r_ary));
}(ary));

console.log(ary);
console.log(ret);