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;
}
//for test
alert(['a','b','c','d','b','a','e'].distinct());