Does Javascript have a contains function?

Question

I am not sure if it does or does not. Some sites show using a contains in javascript but when I try it does not work.

I have

var userAgent = navigator.userAgent.split(';');

if (userAgent.contains("msie7") == true) {...}

I am trying to use the useragent to figure out if the user is running IE 8 in compatibility mode. So I want to check the userAgenet for msie7 & for the trident 4.0

So how could I check this array?

Answer 1

There is no native Array.prototype.contains in ES v3 ( most JS implementations ). There is an Array.prototype.indexOf available in Mozilla/Firefox and other modern JS engines which choose to adopt it.

You can use the code below to implement it on browsers/engines that dont have it: https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/indexOf

Then after assigning it you can do Array.prototype.contains = function(s) { return this.indexOf(s) !== -1 }

Answer 2

You can use indexOf to get the index in the array which contains the element you're looking for. So you could rewrite your if statement like this:

if (userAgent.indexOf("msie7") > -1) {...}

---

Note that IE (at least IE6) doesn't support indexOf for arrays (it does work on strings though), but you could always write your own version:

if (typeof Array.prototype.indexOf == 'undefined')
  Array.prototype.indexOf = function(e) {
    for (var i = 0; i < this.length; i++)
      if (this[i] == e)
        return i;
    return -1;
  }

Answer 3

In the end I found out that jquery has a method called inArary and I used this. So I should not have to worry about compatibility issues.

Answer 4

You can always roll out your own contains() which will work on Array objects on all browsers.

Array.prototype.contains = function(obj) {
    var i = this.length;
    while (i--) {
       if (this[i] === obj) {
          return true;
        } 
    }
    return false;
}

Caveat: "Extending the javascript Array object is a really bad idea because you introduce new properties (your custom methods) into for-in loops which can break existing scripts."

Better use the functions provided by a mainstream library such as jQuery.

Full discussion on this topic: Javascript - array.contains(obj)

Answer 5

Mootools is one library that can help you write better cross browser javascript. It augments javascript basic types( strings , arrays , numbers , etc) with convenient methods like 'contains'.

Or, you can implement it yourself as seen in the other answers.

Answer 6

You could skip the array and test the string directly, like this:

if (navigator.userAgent.indexOf('msie') != -1)
    // ...

Here's some some information on indexOf .