set cursor in end of the word in textbox firefox issue

js:-

function SetEnd(textBox)
{
if (textBox.createTextRange)
{
var fieldRange = textBox.createTextRange();
fieldRange.moveStart('character', textBox.value.length);
fieldRange.collapse();
fieldRange.select();
}
}
C#:-

HttpBrowserCapabilities httpBrowserCapabilities = new HttpBrowserCapabilities();

httpBrowserCapabilities = Request.Browser;

if (httpBrowserCapabilities.Browser != "Firefox")
{
searchTextBox.Attributes.Add("OnFocus", "SetEnd(this)");
}