javascript testing if value is in array

Question

Is there a function in javascript to do this - test if a given value (a string in my case) exists in an array (of strings)? I know I could just loop over each value, but I'm wondering if js has a shorthand for this.

possible duplicate of [Javascript - array.contains(obj)](http://stackoverflow.com/questions/237104/javascript-array-containsobj) — annakata, Oct 01 '10 at 13:07
Indexed arrays may not be the correct data structure if you need to do this frequently. Consider using an associative array / object representation (which affords you the logical `in` operator). — annakata, Oct 01 '10 at 13:09

naugtur · Accepted Answer · 2010-10-01T13:13:05.307

3

jquery has .inArray() method. It's the best I know..

edited Oct 01 '10 at 13:13

answered Oct 01 '10 at 13:00

naugtur

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@bba, you might want to add information like that to your question. And to the **tags** for your question. (Edited your question to add the 'jquery' tag.) – David Thomas Oct 01 '10 at 13:03
@bba - Be sure to tag your question with jQuery if that's the case, it will get very different answers in many cases. :) – Nick Craver Oct 01 '10 at 13:03

score 2 · Answer 2 · answered Oct 01 '10 at 13:01

There's .indexOf() for this, but IE<9 doesn't support it:

if(array.indexOf("mystring") > -1) {
  //found
}

From the same MDC documentation page, here's what to include (before using) to make IE work as well:

if (!Array.prototype.indexOf)
{
  Array.prototype.indexOf = function(elt /*, from*/)
  {
    var len = this.length >>> 0;

    var from = Number(arguments[1]) || 0;
    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);
    if (from < 0)
      from += len;

    for (; from < len; from++)
    {
      if (from in this &&
          this[from] === elt)
        return from;
    }
    return -1;
  };
}

.indexOf() returns the index in the array the string was found at, or -1 if it wasn't found.

score 0 · Answer 3 · answered Oct 01 '10 at 13:20

For functions that are in php and should be in javascript or I haven't found yet I go to: http://phpjs.org

The function you want use if you're just using javascript is in_array here: http://phpjs.org/functions/in_array:432

Otherwise, use the jQuery solution on this page.

javascript testing if value is in array

3 Answers3