JavaScript Reference
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Quick Reference

The JavaScript RegExp lastIndex property specifies the index at which to start the next match, and only works if the g modifier is set.

<!-- html element to place output -->
<p id="my_output"></p>
// variables
let text = 'Hello World, Hello Universe';
let pattern = /llo/g;
let result = '';

while (pattern.test(text) == true)  {
  	result += 'Found at position ' + pattern.lastIndex + '<br>'; // starts the next match directly after the previous match
}

// output to the HTML element
document.getElementById('my_output').innerHTML = result;

Note

In the above example, the g modifier requests a global match, which finds ALL matches, and NOT just the first match.

/regexp/g

Output

Found at position 5
Found at position 18

Note

Arrays count starting from zero NOT one. So item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on.

Syntax

RegExpObject.lastIndex

JavaScript Notes:

  • When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
  • JavaScript is a case-sensitive language; firstName is NOT the same as firstname
  • Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
  • JavaScript variables must begin with a letter, $, or _
  • JavaScript variables are case sensitive (x is not the same as X)
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