This tutorial explains the exec() method in JavaScript, which is used to execute a regular expression on a string and return detailed match information.

Definition and Usage

The exec() method executes a search for a match in a string. It returns an array containing the matched text and any captured groups, or null if no match is found.

Syntax

regexp.exec(string)

Parameters

Parameter	Description
string	The string to search within.

Return Value

Returns an array with the matched text and captured groups, or null if no match is found.

Example

Here's how to use the exec() method:

const regex = /(d{3})-(d{4})/;
const str = "My number is 123-4567.";
const result = regex.exec(str);

console.log(result); // Output: ["123-4567", "123", "4567", index: 14, input: "My number is 123-4567.", groups: undefined]

Key Points

• If the regular expression has no global flag (g), exec() will return the first match.
• If the regular expression has the global flag (g), each call to exec() will return the next match from where the last one left off.
• The returned array includes the full match at index 0, followed by captured groups.
• The index property shows the position of the match in the string.
• The input property contains the original string that was searched.

Practical Use Cases

The exec() method is useful when you need detailed information about matches, such as capturing specific parts of a string (e.g., extracting phone numbers, email addresses, or dates).

Related Methods

• test() – Tests whether a pattern exists in a string.
• match() – Returns all matches of a pattern in a string.
• matchAll() – Returns an iterator of all matches.