Returns the position at which a substring occurs within a string. The function uses 1-based indexing—that is, the first character in the string is counted as position 1. A result of 0 indicates that the substring wasn’t found in the source string.

The IndexOf() function has two parameters:

  • sourceString (string): Required. The string to analyze.
  • substring (string): Required. The character or substring to find the position of.

To use the function, pass it a source string, and the substring that you want to find in that string.

This example finds a single character within a string and returns its position. It uses simple conditional logic to determine which text to output.

The example outputs the result of the function.

This example finds a substring that consists of multiple consecutive characters.

The function returns the position at which the substring begins.