buf.toString([encoding[, start[, end]]])

• encoding <string> 要使用的字符编码。 默认值: 'utf8'。
• start <integer> 开始解码的字节偏移量。 默认值: 0。
• end <integer> 停止解码的字节偏移量（不包括在内）。 默认值: buf.length.
• 返回: <string>

根据 encoding 中指定的字符编码将 buf 解码为字符串。 start 和 end 可以传入仅解码 buf 的子集。

如果 encoding 是 'utf8' 并且输入中的字节序列不是有效的 UTF-8，则每个无效字节都将替换为替换字符 U+FFFD。

字符串实例（以 UTF-16 代码单元表示）的最大长度可用作 buffer.constants.MAX_STRING_LENGTH。

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 是 'a' 的十进制 ASCII 值。
  buf1[i] = i + 97;
}

console.log(buf1.toString('utf8'));
// 打印: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('utf8', 0, 5));
// 打印: abcde

const buf2 = Buffer.from('tést');

console.log(buf2.toString('hex'));
// 打印: 74c3a97374
console.log(buf2.toString('utf8', 0, 3));
// 打印: té
console.log(buf2.toString(undefined, 0, 3));
// 打印: té

• encoding <string> The character encoding to use. Default: 'utf8'.
• start <integer> The byte offset to start decoding at. Default: 0.
• end <integer> The byte offset to stop decoding at (not inclusive). Default: buf.length.
• Returns: <string>

Decodes buf to a string according to the specified character encoding in encoding. start and end may be passed to decode only a subset of buf.

If encoding is 'utf8' and a byte sequence in the input is not valid UTF-8, then each invalid byte is replaced with the replacement character U+FFFD.

The maximum length of a string instance (in UTF-16 code units) is available as buffer.constants.MAX_STRING_LENGTH.

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

console.log(buf1.toString('utf8'));
// Prints: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('utf8', 0, 5));
// Prints: abcde

const buf2 = Buffer.from('tést');

console.log(buf2.toString('hex'));
// Prints: 74c3a97374
console.log(buf2.toString('utf8', 0, 3));
// Prints: té
console.log(buf2.toString(undefined, 0, 3));
// Prints: té