PHP's is_unicode in JavaScript

How to use

You you can install via yarn add locutus and require this function via const is_unicode = require('locutus/php/var/is_unicode').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.


Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#codeexpected result
1is_unicode('We the peoples of the United Nations...!')true


  • Almost all strings in JavaScript should be Unicode

Here’s what our current JavaScript equivalent to PHP's is_unicode looks like.

module.exports = function is_unicode(vr) {
// discuss at:
// original by: Brett Zamir (
// note 1: Almost all strings in JavaScript should be Unicode
// example 1: is_unicode('We the peoples of the United Nations...!')
// returns 1: true

if (typeof vr !== 'string') {
return false

// If surrogates occur outside of high-low pairs, then this is not Unicode
let arr = []
const highSurrogate = '[\uD800-\uDBFF]'
const lowSurrogate = '[\uDC00-\uDFFF]'
const highSurrogateBeforeAny = new RegExp(highSurrogate + '([\\s\\S])', 'g')
const lowSurrogateAfterAny = new RegExp('([\\s\\S])' + lowSurrogate, 'g')
const singleLowSurrogate = new RegExp('^' + lowSurrogate + '$')
const singleHighSurrogate = new RegExp('^' + highSurrogate + '$')

while ((arr = highSurrogateBeforeAny.exec(vr)) !== null) {
if (!arr[1] || !arr[1].match(singleLowSurrogate)) {
// If high not followed by low surrogate
return false
while ((arr = lowSurrogateAfterAny.exec(vr)) !== null) {
if (!arr[1] || !arr[1].match(singleHighSurrogate)) {
// If low not preceded by high surrogate
return false

return true

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

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