substring

Returns a subset of a String object.

Applies to

String

Syntax

substring(indexA, indexB)

Parameters

indexA

An integer between 0 and 1 less than the length of the string.

indexB

An integer between 0 and 1 less than the length of the string.

Description

substring extracts characters from indexA up to but not including indexB. In particular:

If indexA is less than 0, indexA is treated as if it were 0.
If indexB is greater than stringName.length, indexB is treated as if it were stringName.length.
If indexA equals indexB, substring returns an empty string.
If indexB is omitted, substring extracts characters to the end of the string.
If indexA is greater than indexB, JavaScript returns a substring beginning with indexB and ending with indexA - 1.

Examples

The following example uses substring to display characters from the string "Netscape":

var anyString="Netscape"
//Displays "Net"
Console.Write(anyString.substring(0,3))
Console.Write(anyString.substring(3,0))
//Displays "cap"
Console.Write(anyString.substring(4,7))
Console.Write(anyString.substring(7,4))
//Displays "Netscap"
Console.Write(anyString.substring(0,7))
//Displays "Netscape"
Console.Write(anyString.substring(0,8))
Console.Write(anyString.substring(0,10))

The following example replaces a substring within a string. It will replace both individual characters and substrings. The function call at the end of the example changes the string "Brave New World" into "Brave New Web".

function replaceString(oldS,newS,fullS) {
// Replaces oldS with newS in the string fullS
      for (var i=0; i<fullS.length; i++) {
            if (fullS.substring(i,i+oldS.length) == oldS) {
                  fullS = fullS.substring(0,i)+newS+fullS.substring(i+oldS.length,fullS.length)
            }
      }
      return fullS
}
replaceString("World","Web","Brave New World")