Actionscript Cookbook

9.4. Searching for a Substring

Problem

You want to find a value within a string.

Solution

Use the indexOf( ) or lastIndexOf( ) methods.

Discussion

You can use the indexOf( ) and lastIndexOf( ) methods to determine whether a string contains a specified substring value. Each method returns the starting index of the substring if it is found. If the substring is not found, the value -1 is returned.

The indexOf( ) method takes up to two parameters:

substring

The substring value for which you want to search.

startIndex

The zero-relative starting position from which to search within the string. If undefined, the method begins the search from the beginning of the string.

If you want to test whether a string contains another string, you can use the indexOf( ) method with only one parameter. For example:

myString = "This string contains the word cool twice. Very cool!";

// Get the index of the first occurrence of the substring "cool" within myString. 
indexOfCool = myString.indexOf("cool");

// If the indexOf(  ) method returns -1, no occurrences of "cool" were found.
if (indexOfCool != -1) {
  // Displays: "String contains word cool at index 30", because the first occurrence
  // of the substring appears starting at index 30 within myString.
  trace("String contains word cool at index " + indexOfCool);
}

You can get the indexes of subsequent occurrences of a substring by specifying the second, optional parameter of the indexOf( ) method, StartIndex. A simple and effective way to search for the next ...