How does javascript determine whether elements in an array are repeated? collection _ javascript skills

How does javascript judge whether the elements in the Array are repeated? var str = new Array ();
For example, there is an array with 20 18-digit ID card numbers.
Check whether the ID card number is repeated.
How to quickly determine?

The Code is as follows:

Var ary = new Array ("111", "22", "33", "111 ");
Var s = ary. join (",") + ",";
For (var I = 0; I {
If (s. replace (ary [I] + ",", ""). indexOf (ary [I] + ",")>-1)
{
Alert ("repeated! ");
}
}

The Code is as follows:

Var ary = new Array ("111", "22", "33", "111 ");
Var nary = ary. sort ();
For (var I = 0; I {If (nary [I] = nary [I + 1])
{Alert ("repeated content:" + nary [I]);}
}

Use the \ 1 in the regular expression (the first matching result)
First use join () to convert the array into a string and the separator \ x0f specified by the plug (this separator is generally not input). This step is purely for simplified and accurate scripts.
This mode is the trick I came up with when writing MzTreeView, and can skip the for loop to achieve extreme efficiency.

The Code is as follows:

Var hash = {};
For (var I in arr ){
If (hash [arr [I])
Return true;
Hash [arr [I] = true;
}
Return false;

<Script language = "JavaScript"> <! -- Function mm (a) {return/(\ x0f [^ \ x0f] +) \ x0f [\ s \ S] * \ 1 /. test ("\ x0f" +. join ("\ x0f \ x0f") + "\ x0f");} var ary = new Array ("111", "22", "33", "112 ", "22"); alert (mm (ary) // --> SCRIPT
[Ctrl + A select all Note: If you need to introduce external Js, You need to refresh it to execute]