等同于java的String.getBytes方法

getBytes.ts

function strToUtf8Bytes(str = '') {
    const utf8: number[] = [];
    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++;
        // Surrogate pair:
        // UTF-16 encodes 0x10000-0x10FFFF by subtracting 0x10000 and
        // splitting the 20 bits of 0x0-0xFFFFF into two halves
        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),
        );
      }
    }
    //兼容汉字，ASCII码表最大的值为127，大于127的值为特殊字符，【下面不必要，结果是有符号数，需要通过new Uint8Array()处理一次】
//     for(let j=0; j<utf8.length; j++){
//         const code = utf8[j];
//         if(code>127){
//             utf8[j] = code - 256;
//         }
//     }
    return utf8;
  }