js+中文转码utf+8

function toUTF8Array(str) {
    const utf8 = [];
    for (let i = 0; i < str.length; i++) {
        let charCode = str.charCodeAt(i);
        if (charCode < 0x80) {
            utf8.push(charCode);
        } else if (charCode < 0x800) {
            utf8.push(0xc0 | (charCode >> 6), 0x80 | (charCode & 0x3f));
        } else if (charCode < 0xd800 || charCode >= 0xe000) {
            utf8.push(0xe0 | (charCode >> 12), 0x80 | ((charCode >> 6) & 0x3f), 0x80 | (charCode & 0x3f));
        } else {
            i++;
            charCode = 0x10000 + (((charCode & 0x3ff) << 10) | (str.charCodeAt(i) & 0x3ff));
            utf8.push(0xf0 | (charCode >> 18), 0x80 | ((charCode >> 12) & 0x3f), 0x80 | ((charCode >> 6) & 0x3f), 0x80 | (charCode & 0x3f));
        }
    }
    return utf8;
}

const chineseStr = "你好，世界！";
const utf8Bytes = toUTF8Array(chineseStr);
console.log(utf8Bytes);