I have the following code:

        var currentServerlist = [];
        var newServerIp = document.getElementById('add_server').value; 
        if( CurrentServerIP != newServerIp )
        {
            $('#failoverServers td.row_selector').each(function() {
            var row = $(this).closest('tr');
            var serverIp = row.find('td[rel=ip]').text();
            currentServerlist.push(serverIp);   
            });

            if(currentServerlist.lastIndexOf(newServerIp) != -1)
            {
                return true;
            }
            return false;
         }

But I find that the lastIndexOf does not work in InternetExplorer (It does in Chrome).

How can I fix this?

I have the following code:

        var currentServerlist = [];
        var newServerIp = document.getElementById('add_server').value; 
        if( CurrentServerIP != newServerIp )
        {
            $('#failoverServers td.row_selector').each(function() {
            var row = $(this).closest('tr');
            var serverIp = row.find('td[rel=ip]').text();
            currentServerlist.push(serverIp);   
            });

            if(currentServerlist.lastIndexOf(newServerIp) != -1)
            {
                return true;
            }
            return false;
         }

But I find that the lastIndexOf does not work in InternetExplorer (It does in Chrome).

How can I fix this?

• javascript

• According to W3School, lastIndexOf is supported by IE : w3schools./jsref/jsref_lastindexof.asp – sdespont Commented Feb 7, 2013 at 9:33
• 7 @sdespont, would not be the first time w3schools was wrong – epoch Commented Feb 7, 2013 at 9:35

3 Answers 3

According to the ES5 patability table, Array.prototype.lastIndexOf is supported in all browsers except IE8 and below.

If you need to support such browsers, you can use one of the various polyfills that are available (or a more plete ES5 polyfill solution).

Some browsers (IE) don't support a lot of JavaScript properties. I usually find a solution on mdn:

https://developer.mozilla/en-US/docs/JavaScript/Reference/Global_Objects/Array/lastIndexOf

The code there:

if (!Array.prototype.lastIndexOf)
{
  Array.prototype.lastIndexOf = function(searchElement /*, fromIndex*/)
  {
    "use strict";

    if (this == null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (len === 0)
      return -1;

    var n = len;
    if (arguments.length > 1)
    {
      n = Number(arguments[1]);
      if (n != n)
        n = 0;
      else if (n != 0 && n != (1 / 0) && n != -(1 / 0))
        n = (n > 0 || -1) * Math.floor(Math.abs(n));
    }

    var k = n >= 0
          ? Math.min(n, len - 1)
          : len - Math.abs(n);

    for (; k >= 0; k--)
    {
      if (k in t && t[k] === searchElement)
        return k;
    }
    return -1;
  };
}

lastIndexOf seems only be implemented in IE9/10. You need to use a shim to support it. See: ES5-shim, line 509-535 in particular.