Javascript’s Unicode Problem

Disclaimer: A repost of my article for CafeDev

A while ago I needed a sim­ple string pad func­tion, and since it’s a freak­ishly sim­ple task, I just wrote a sim­ple func­tion:

function limit(str, limit = 16, padString = "#", padPosition = "right") {
    const strLength = str.length;

    if (strLength > limit) {
        return str.substring(0, limit);
    } else if (strLength < limit) {
        const padRepeats = padString.repeat(limit - strLength);
        return (padPosition === "left") ? padRepeats + str : str + padRepeats;
    return str;

Pretty sim­ple, right? And it works too… Until you add in an emoji to your text. Then every­thing falls apart and worlds col­lide! How? Simple:

"💩".length // 2!

(If you’re read­ing this on Linux you might ac­tu­ally see 2 bro­ken uni­code char­ac­ters, and the re­sult makes sense un­less you have in­stalled an emoji pack­age on your browser or OS)...

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