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import { isHighSurrogate, isLowSurrogate } from '@adecore/utils/text';

A character outside the Basic Multilingual Plane, such as most emoji, takes two UTF-16 code units in a JavaScript string: a high surrogate and a low one. Cutting between them leaves a broken character.

isHighSurrogate(code) and isLowSurrogate(code) take a code unit from charCodeAt. Check them before you cut a string at an offset:

function truncate(text: string, length: number): string {
    if (text.length <= length) {
        return text;
    }

    const end = isHighSurrogate(text.charCodeAt(length - 1)) ? length - 1 : length;

    return text.slice(0, end);
}