4 ways to repeat an array in JavaScript

The first: It is also the most stupid.

Array.prototype.unique1 = function () {
var r = new Array ();
Label:for (var i = 0, n = this.length; i < n; i++) {
for (var x = 0, y = r.length < y; x + +) {
if (r[x] = = This[i]) {
Continue label;
}
}
R[r.length] = this[i];
}
return R;
}
The second kind: This is the same as the heavenly book.

Array.prototype.unique2 = function () {
Return This.sort (). Join (",,"). Replace (/(, |^) ([^,]+) (,, \2) + (, |$)/g, "$1$2$4"). Replace (/,,+/g, ","). Replace (/,$/, "" " ). Split (",");
}
Third: Using the "hasOwnProperty" method of the object

Array.prototype.unique3 = function () {
var temp = {}, len = This.length;
for (Var i=0 i < Len; i++) {
var tmp = this[i];
if (!temp.hasownproperty (TMP)) {
Temp[this[i]] = "My God";
}
}

len = 0;
var temparr=[];
for (var i in temp) {
temparr[len++] = i;
}
return Temparr;
}

The fourth kind: first sort, the preceding paragraph is more than bottom. This method is very simple, but also practical

Array.prototype.unique4 = function () {
var temp = new Array ();
This.sort ();
for (i = 0; i < this.length; i++) {
if (this[i] = = This[i+1]) {
Continue
}
Temp[temp.length]=this[i];
}
return temp;

}

The following is used frequently, and the efficiency is also very good. Kind of like a hash table feeling.

Array.prototype.unique5 = function () {
var res = [], hash = {};
For (var i=0, Elem; (Elem = this[i])!= null; i++) {
if (!hash[elem])
{
Res.push (Elem);
Hash[elem] = true;
}
}
return res;
}