libphonenumber-js/source/helpers/getIddPrefix.js

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

import Metadata from '../metadata.js'

/**
 * Pattern that makes it easy to distinguish whether a region has a single
 * international dialing prefix or not. If a region has a single international
 * prefix (e.g. 011 in USA), it will be represented as a string that contains
 * a sequence of ASCII digits, and possibly a tilde, which signals waiting for
 * the tone. If there are multiple available international prefixes in a
 * region, they will be represented as a regex string that always contains one
 * or more characters that are not ASCII digits or a tilde.
 */
const SINGLE_IDD_PREFIX_REG_EXP = /^[\d]+(?:[~\u2053\u223C\uFF5E][\d]+)?$/

// For regions that have multiple IDD prefixes
// a preferred IDD prefix is returned.
export default function getIddPrefix(country, callingCode, metadata) {
	const countryMetadata = new Metadata(metadata)
	countryMetadata.selectNumberingPlan(country, callingCode)
	if (countryMetadata.defaultIDDPrefix()) {
		return countryMetadata.defaultIDDPrefix()
	}
	if (SINGLE_IDD_PREFIX_REG_EXP.test(countryMetadata.IDDPrefix())) {
		return countryMetadata.IDDPrefix()
	}
}