JavaScript by Example

Working with regular expressions in JavaScript

Regular expressions (RegExp) are basically a definition of a pattern (such as a sequence of characters, numbers, and so on) that can be searched within other text. For example, say you need to find all the words in a paragraph that start with the letter a. Then, in JavaScript, you define the pattern as:

const pattern = /^a+/

Regular expressions are always defined inside / /. In the preceding code snippet, we have the following:

• ^ means in the beginning of
• + means having at least one

This regular expression will match strings that start with the letter a. You can test these statements in: https://jsfiddle.net/. To test a string with this regular expression, do the following:

pattern.test('alpha') ...