buf.fill(value[, offset[, end]][, encoding])

• value <string> | <Buffer> | <Uint8Array> | <integer> 用于填充 buf 的值。 空值（字符串、Uint8Array、缓冲区）被强制转换为 0。
• offset <integer> 在开始填充 buf 之前要跳过的字节数。 默认值: 0。
• end <integer> 停止填充 buf（不包括在内）的位置。 默认值: buf.length.
• encoding <string> 如果 value 是字符串，则为 value 的编码。 默认值: 'utf8'。
• 返回: <Buffer> buf 的引用。

用指定的 value 填充 buf。 如果没有给定 offset 和 end，则整个 buf 都会被填满：

import { Buffer } from 'node:buffer';

// 用 ASCII 字符 'h' 填充 `Buffer`。

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// 打印: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// 用空字符串填充缓冲区
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// 打印: <Buffer 00 00 00 00 00>const { Buffer } = require('node:buffer');

// 用 ASCII 字符 'h' 填充 `Buffer`。

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// 打印: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// 用空字符串填充缓冲区
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// 打印: <Buffer 00 00 00 00 00>

如果 value 不是字符串、Buffer 或整数，则将其强制为 uint32 值。 如果结果整数大于 255（十进制），则 buf 将填充 value & 255。

如果 fill() 操作的最终写入落在多字节字符上，则仅写入适合 buf 的该字符的字节：

import { Buffer } from 'node:buffer';

// 用在 UTF-8 中占用两个字节的字符填充 `Buffer`。

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// 打印: <Buffer c8 a2 c8 a2 c8>const { Buffer } = require('node:buffer');

// 用在 UTF-8 中占用两个字节的字符填充 `Buffer`。

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// 打印: <Buffer c8 a2 c8 a2 c8>

如果 value 包含无效字符，则截断；如果没有有效的填充数据，则抛出异常：

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(5);

console.log(buf.fill('a'));
// 打印: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// 打印: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// 抛出异常。const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(5);

console.log(buf.fill('a'));
// 打印: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// 打印: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// 抛出异常。

• value <string> | <Buffer> | <Uint8Array> | <integer> The value with which to fill buf. Empty value (string, Uint8Array, Buffer) is coerced to 0.
• offset <integer> Number of bytes to skip before starting to fill buf. Default: 0.
• end <integer> Where to stop filling buf (not inclusive). Default: buf.length.
• encoding <string> The encoding for value if value is a string. Default: 'utf8'.
• Returns: <Buffer> A reference to buf.

Fills buf with the specified value. If the offset and end are not given, the entire buf will be filled:

import { Buffer } from 'node:buffer';

// Fill a `Buffer` with the ASCII character 'h'.

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// Fill a buffer with empty string
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// Prints: <Buffer 00 00 00 00 00>const { Buffer } = require('node:buffer');

// Fill a `Buffer` with the ASCII character 'h'.

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// Fill a buffer with empty string
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// Prints: <Buffer 00 00 00 00 00>

value is coerced to a uint32 value if it is not a string, Buffer, or integer. If the resulting integer is greater than 255 (decimal), buf will be filled with value & 255.

If the final write of a fill() operation falls on a multi-byte character, then only the bytes of that character that fit into buf are written:

import { Buffer } from 'node:buffer';

// Fill a `Buffer` with character that takes up two bytes in UTF-8.

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// Prints: <Buffer c8 a2 c8 a2 c8>const { Buffer } = require('node:buffer');

// Fill a `Buffer` with character that takes up two bytes in UTF-8.

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// Prints: <Buffer c8 a2 c8 a2 c8>

If value contains invalid characters, it is truncated; if no valid fill data remains, an exception is thrown:

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(5);

console.log(buf.fill('a'));
// Prints: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// Prints: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// Throws an exception.const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(5);

console.log(buf.fill('a'));
// Prints: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// Prints: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// Throws an exception.