参考答案:

Array.prototype.distinct = function() {    var ret = [];    for (var i = 0; i < this.length; i++) {        for (var j = i + 1; j < this.length;) {            if (this[i] === this[j]) {                ret.push(this.splice(j, 1)[0]);            } else {                j++;            }        }    }    return ret;};let arr = ["a", "b", "c", "d", "b", "a", "e"];console.log(arr.distinct()); // ['a', 'b']console.log(arr); // ['a', 'b', 'c', 'd', 'e']