String.prototype.substring()

The substring() method returns the part of the string from the start index up to and excluding the end index, or to the end of the string if no end index is supplied.

Syntax

substring(indexStart)
substring(indexStart, indexEnd)

Parameters

• indexStart
  • : The index of the first character to include in the returned substring.
• indexEnd optional
  • : The index of the first character to exclude from the returned substring.

Return value

A new string containing the specified part of the given string.

Description

substring() extracts characters from indexStart up to but not including indexEnd. In particular:

• If indexEnd is omitted, substring() extracts characters to the end of the string.
• If indexStart is equal to indexEnd, substring() returns an empty string.
• If indexStart is greater than indexEnd, then the effect of substring() is as if the two arguments were swapped; see example below.

Any argument value that is less than 0 or greater than str.length is treated as if it were 0 and str.length, respectively.

Any argument value that is NaN is treated as if it were 0.