RegExp.prototype.exec()

The exec() method of RegExp instances executes a search with this regular expression for a match in a specified string and returns a result array, or null.

JavaScript RegExp objects are stateful when they have the global or sticky flags set (e.g., /foo/g or /foo/y). They store a lastIndex from the previous match. Using this internally, exec() can be used to iterate over multiple matches in a string of text (with capture groups), as opposed to getting just the matching strings with String.prototype.match().

When using exec(), the global flag has no effect when the sticky flag is set — the match is always sticky.

Syntax example: exec(str)