如何进行编解码操作，有人知道吗？

//将字节数组解码成字符串 
let textDecoderOptions: util.TextDecoderOptions = { 
  fatal: false, 
  ignoreBOM : true 
} 
let decodeWithStreamOptions: util.DecodeWithStreamOptions = { 
  stream: false 
} 
let textDecoder = util.TextDecoder.create('utf-8', textDecoderOptions); 
let result = new Uint8Array(6); 
result[0] = 0xEF; 
result[1] = 0xBB; 
result[2] = 0xBF; 
result[3] = 0x61; 
result[4] = 0x62; 
result[5] = 0x63; 
console.info("input num:"); 
let retStr = textDecoder.decodeWithStream(result , decodeWithStreamOptions); 
console.info("retStr = " + retStr);

//将字符串编码为字节数组 
let textEncoder = new util.TextEncoder(); 
let buffer = new ArrayBuffer(20); 
let result = new Uint8Array(buffer); 
result = textEncoder.encodeInto("\uD800¥¥");