libphonenumber-js/source/helpers/extension/extractExtension.js

A simpler (and smaller) rewrite of Google Android's libphonenumber library in javascript

import createExtensionPattern from './createExtensionPattern.js'

// Regexp of all known extension prefixes used by different regions followed by
// 1 or more valid digits, for use when parsing.
const EXTN_PATTERN = new RegExp('(?:' + createExtensionPattern() + ')$', 'i')

// Strips any extension (as in, the part of the number dialled after the call is
// connected, usually indicated with extn, ext, x or similar) from the end of
// the number, and returns it.
export default function extractExtension(number) {
	const start = number.search(EXTN_PATTERN)
	if (start < 0) {
		return {}
	}
	// If we find a potential extension, and the number preceding this is a viable
	// number, we assume it is an extension.
	const numberWithoutExtension = number.slice(0, start)
	const matches = number.match(EXTN_PATTERN)
	let i = 1
	while (i < matches.length) {
		if (matches[i]) {
			return {
				number: numberWithoutExtension,
				ext: matches[i]
			}
		}
		i++
	}
}