jquery split() and indexOf results in "Object doesn't support this property or method"

Question

I have the following code:

var selected = $('#hiddenField').val().split(",");
...
if (selected.indexOf(id) > 0) {
   ... set value ...
}

I'm dynamically creating a CheckBoxList, and trying to remember the state of the checkboxes by putting the selected IDs into the hidden field.

I get an error stating that "Object doesn't support this property or method". My assumption is that selected is an array, which should support indexOf. Is that incorrect?

Answer 1

Based on your error message, I'm assuming this is coming from Internet Explorer.

Surprise! Internet Explorer (including version 8) does not support indexOf for arrays.

Here is Firefox's implementation you can use:

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;
  };
}

Answer 2

indexOf is not a standard a method on the Array object; but it is on the String object.

You're fine without using split;

if ($('#hiddenField').val().indexOf(id) > -1) {
  // set it
}

Be very careful with indexOf; a return of zero means that the character exists, and it's first occurance is the first character. It returns -1 if the string wasn't found.

If you still fancy using your array, you'll have to iterate over selected using a good old fashioned for loop.

Answer 3

[].indexOf || (Array.prototype.indexOf = function(v,n){
  n = (n==null)?0:n; var m = this.length;
  for(var i = n; i < m; i++)
    if(this[i] == v)
       return i;
  return -1;
});

Answer 4

.indexOf() is a string method. There is no such method for arrays. However if the IDs are totally distinct and are all of the same length (e.g. 3 digits) you can just do:

if ($('#hiddenField').val().indexOf(id) > -1) {
   ... set value ...
}

Of course it does not work if you have IDs like 128 and 12.

Answer 5

There's an jQuery method to overcome the lack of indexOf(), you can use .inArray() instead:

var selected = $('#hiddenField').val().split(",");
if ($.inArray(id, selected) > -1) {
   ... set value ...
}

jQuery.inArray() exists for just this reason...if you're including jQuery already, no need to write the function again. Note: This actually returns a number, like indexOf() would.