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index Property (JavaScript)

Returns the character position where the first successful match begins in a searched string. Read-only.

RegExp.index 

The object associated with this property is always the global RegExp object.

The index property is zero-based. The initial value of the index property is –1. Its value changes whenever a successful match is made.

The following example illustrates the use of the index property. This function iterates a search string and prints out the index and lastIndex values for each word in the string.

function RegExpTest()
{
   var ver = Number(ScriptEngineMajorVersion() + "." + ScriptEngineMinorVersion())
   if (ver < 5.5)
   {
      document.write("You need a newer version of JavaScript for this to work");
      return;
   }

   var src = "The quick brown fox jumps over the lazy dog.";

   // Create regular expression pattern with a global flag.
   var re = /\w+/g;

   // Get the next word, starting at the position of lastindex.
   var arr;
   while ((arr = re.exec(src)) != null)
      {
      // New line:
      document.write ("<br />");  
      document.write (arr.index + "-" + arr.lastIndex + " ");
      document.write (arr);
      }
}

Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards. See Version Information.

Applies To: RegExp Object (JavaScript)

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