stream-chat-react/dist/utils/getWholeChar.js

React components to create chat conversations or livestream style chat

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charAt#getting_whole_characters
export const getWholeChar = (str, i) => {
    const code = str.charCodeAt(i);
    if (Number.isNaN(code))
        return '';
    if (code < 0xd800 || code > 0xdfff)
        return str.charAt(i);
    if (0xd800 <= code && code <= 0xdbff) {
        if (str.length <= i + 1) {
            throw 'High surrogate without following low surrogate';
        }
        const next = str.charCodeAt(i + 1);
        if (0xdc00 > next || next > 0xdfff) {
            throw 'High surrogate without following low surrogate';
        }
        return str.charAt(i) + str.charAt(i + 1);
    }
    if (i === 0) {
        throw 'Low surrogate without preceding high surrogate';
    }
    const prev = str.charCodeAt(i - 1);
    if (0xd800 > prev || prev > 0xdbff) {
        throw 'Low surrogate without preceding high surrogate';
    }
    return '';
};