JavaScript lastIndexOf() method

The lastIndexOf() method belongs to JavaScript's String object: it searches a string backward, for the last instance of characters you pass as argument; if the match occurs only once, there is no difference with its sister method, indexOf(). If found, the character position index is returned: var str = "I learn JavaScript, and learning is fun"; alert( str.lastIndexOf("learn") ); // returns 24
Remember that the first character position index is zero, not 1 - here's a different search: var str = "I learn JavaScript, and learning is fun"; alert( str.lastIndexOf("I learn") ); // Found at beginning: returns 0
lastIndexOf() returns "-1" when no match is found in the string: var str = "I learn JavaScript"; alert( str.lastIndexOf("carrot") ); // Not found: returns -1
You can use the method on variables, literals, and any kind of text found on web pages, like HTML form elements' values, or other elements' innerHTML. Here's how you test against a literal: alert( "I learn JavaScript".lastIndexOf("ear") ); // returns 3
Because lastIndexOf() is case-sensitive, you'll need toLowerCase() or toUpperCase() for a case-insensitive search: due to capitalization, the first alert doesn't return what you might expect. var str = "I learn JavaScript right now. Learning is fun"; alert( str.lastIndexOf("learn") ); // Returns 2, first instance alert( str.toLowerCase().lastIndexOf("learn") ); // Returns 30
You can start searching *after* the beginning of the string, which is very practical for indexOf(), but often of limited use for lastIndexOf(), because the optional start index cannot be negative. alert( "I learn JavaScript".lastIndexOf("ear", 5) ); // returns 3
The PHP equivalent to JavaScript's lastIndexOf() method is the strrpos() function: note the second "r", for "reverse"; strpos() -just one "r"- acts like the indexOf() method. PHP handles case-insensitivity with the strripos() function that disregards capitalization when searching: $str = 'I learn PHP right now. Learning is fun'; echo strrpos( $str , 'learn' ); // Returns 2, the first instance echo strripos( $str , 'learn' ); // Returns 23, the last instance
Sister method: indexOf() also searches for one string in another, but starts at the beginning.

Email AOL Mail Gmail Hotmail Yahoo Mail MS Office Excel 2010 OneNote 2010 Outlook 2010 Word 2010 OS & Devices Kindle Fire Windows 7 Web Dev C# and .NET JavaScript jQuery