Why is indexOf not working in Internet Explorer?

Question

This function executes during the forms onSubmit, and works fine in Firefox and Chrome, but not in IE. I suspect it's indexOf, but I cannot seem to find a way to get it to work.

function checkSuburbMatch(e) {

var theSuburb = document.getElementById('suburb').value;
var thePostcode = document.getElementById('postcode').value;

var arrayNeedle = theSuburb + " (" + thePostcode + ")";

if(suburbs.indexOf(arrayNeedle) != -1) {
    alert("Suburb and Postcode match!");
    return false;
} else {
    alert("Suburb and Postcode do not match!");
    return false;
}

}

Swirly

What does variable "suburbs" contain? – Mendelevium

It's an array of strings going along the lines of "suburbName (postCode)" – Swirly

possible duplicate of Why doesn't indexOf work on an array IE8?. See also: How to fix Array indexOf() in JavaScript for IE browsers, Array indexOf implementation for Internet Explorer – Mako

For a thorough explanation of the issue as well as a work around not only for indexOf but the other missing array functions in IE check out the StackOverflow question #2790501 – Egon

FWIW I have a Dev environment where it works with IE11, but when I promoted to my Test environment it stopped working?!?! So it's like IE has a half-baked implementation out there somewhere – Corpuscle

Answer 1

IE simply doesn't have this method on Array, you can add it yourself though, from MDC:

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;
  };
}

This adds .indexOf() if it's missing (at this point that means you're in IE<9) then you can use it. As for why even IE8 doesn't have this already? I can't help you there...

Groan

This didn't seem to work, and made it stop working in Firefox too. Does this need to be placed after the function is called or at the start of the script? – Swirly

@David: It needs to be declared before it is called. – Presbyter

Answer 2

If you are already using jQuery in your project you can use $.inArray()

http://api.jquery.com/jQuery.inArray/

Enrica

Answer 3

indexOf() on MSIE 11 and others it doesn't like non-string variables. On suburbs add .toString() and it should fix it.

Fronia

Answer 4

this function is bad when using associative arrays.

if you put that function in your code and do this

var a = new Array();

a["one"] = "1";

for(var i in a){

   alert(i)

}

You get 0, indexOf which means you inserted indexOf as a key to every array you create

but the array should only have one key and that is "one"

use jQuery!

-Mekias

Mammillate