js去除数组重复

这个算法确实经典，做个笔记。

<script>

Array.prototype.unique = function() {
    for( var a={}, i=0; i<this.length; i++ ) {
        if( typeof( a[ this[i] ] ) === "undefined" ) {
            a[ this[i] ] = 1;  // a.1 = 1, a.2 = 1, a.3 = 1
        }
    }
    this.length=0;
    for(i in a) {
        this[this.length] = i;  // arr[ 0 ] = 1, arr[ 1 ] = 2;
    }
    return this;
}

var a = [1,2,2,3,3,3,4,4,4,4,5,5,5,5,5,6,6,6,6,6,6,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8,11];

document.write(a);  // 1,2,2,3,3,3,4,4,4,4,5,5,5,5,5,6,6,6,6,6,6,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8,11

document.write(a.unique());  // 1,2,3,4,5,6,7,8,11 

</script>