UTF-8

const utf8 = {
    encode: (string, output = []) => {
        const {length} = string;
        let j = 0;
        for (let i=0; i<length; ++i) {
            const code = string.charCodeAt(i);
            if (code < (0b10000000)) {
                output[j++] = code;
            } else if (code < (1 << 11)) {
                output[j++] = 0b11000000|(code >>> 6);
                output[j++] = 0b10000000|(code & 0b00111111);
            } else {
                output[j++] = 0b11100000|(code >>> 12);
                output[j++] = 0b10000000|((code >>> 6) & 0b00111111);
                output[j++] = 0b10000000|(code & 0b00111111);
            }
        }
        return output;
    },
    decode: (bytes) => {
        let i = 0;
        let string = '';
        const {length} = bytes;
        while (i < length) {
            const code = bytes[i++];
            if (code < 0b10000000) {
                string += String.fromCharCode(code);
            } else if (code < 0b11100000) {
                string += String.fromCharCode(((code & 0b00011111) << 6)
                    |(bytes[i++] & 0b00111111));
            } else {
                const mid = bytes[i++];
                string += String.fromCharCode(((code & 0b00011111) << 12)
                    |((mid & 0b00111111) << 6)
                    |(bytes[i++] & 0b00111111));
            }
        }
        return string;
    }
};