buf.lastIndexOf(value[, byteOffset][, encoding])

• value <string> | <Buffer> | <Uint8Array> | <integer> 要搜索的内容。
• byteOffset <integer> 开始搜索 buf 的位置。 如果为负数，则从 buf 的末尾开始计算偏移量。 默认值: buf.length - 1。
• encoding <string> 如果 value 是字符串，则这是用于确定将在 buf 中搜索的字符串的二进制表示的编码。 默认值: 'utf8'。
• 返回: <integer> buf 中最后一次出现 value 的索引，如果 buf 不包含 value，则为 -1。

与 buf.indexOf() 相同，除了找到最后一次出现的 value 而不是第一次出现。

import { Buffer } from 'node:buffer';

const buf = Buffer.from('this buffer is a buffer');

console.log(buf.lastIndexOf('this'));
// 打印: 0
console.log(buf.lastIndexOf('buffer'));
// 打印: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// 打印: 17
console.log(buf.lastIndexOf(97));
// 打印: 15 （97 是 'a' 的十进制 ASCII 值）
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// 打印: -1
console.log(buf.lastIndexOf('buffer', 5));
// 打印: 5
console.log(buf.lastIndexOf('buffer', 4));
// 打印: -1

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// 打印: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// 打印: 4const { Buffer } = require('node:buffer');

const buf = Buffer.from('this buffer is a buffer');

console.log(buf.lastIndexOf('this'));
// 打印: 0
console.log(buf.lastIndexOf('buffer'));
// 打印: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// 打印: 17
console.log(buf.lastIndexOf(97));
// 打印: 15 （97 是 'a' 的十进制 ASCII 值）
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// 打印: -1
console.log(buf.lastIndexOf('buffer', 5));
// 打印: 5
console.log(buf.lastIndexOf('buffer', 4));
// 打印: -1

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// 打印: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// 打印: 4

如果 value 不是字符串、数字或 Buffer，则此方法将抛出 TypeError。 如果 value 是数字，则它将被强制转换为有效的字节值（0 到 255 之间的整数）。

如果 byteOffset 不是数字，则会被强制为数字。 任何强制到 NaN 的参数，如 {} 或 undefined，都将搜索整个缓冲区。 此行为与 String.prototype.lastIndexOf() 匹配。

import { Buffer } from 'node:buffer';

const b = Buffer.from('abcdef');

// 传入数字值，但不是有效字节。
// 打印: 2, 相当于搜索 99 或 'c'。
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));

// 传入强制为 NaN 的 byteOffset。
// 打印: 1, 搜索整个缓冲区。
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));

// 传递强制为 0 的 byteOffset。
// 打印: -1, 相当于传入 0。
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));const { Buffer } = require('node:buffer');

const b = Buffer.from('abcdef');

// 传入数字值，但不是有效字节。
// 打印: 2, 相当于搜索 99 或 'c'。
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));

// 传入强制为 NaN 的 byteOffset。
// 打印: 1, 搜索整个缓冲区。
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));

// 传递强制为 0 的 byteOffset。
// 打印: -1, 相当于传入 0。
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));

如果 value 为空字符串或空 Buffer，则返回 byteOffset。

• value <string> | <Buffer> | <Uint8Array> | <integer> What to search for.
• byteOffset <integer> Where to begin searching in buf. If negative, then offset is calculated from the end of buf. Default: buf.length - 1.
• encoding <string> If value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf. Default: 'utf8'.
• Returns: <integer> The index of the last occurrence of value in buf, or -1 if buf does not contain value.

Identical to buf.indexOf(), except the last occurrence of value is found rather than the first occurrence.

import { Buffer } from 'node:buffer';

const buf = Buffer.from('this buffer is a buffer');

console.log(buf.lastIndexOf('this'));
// Prints: 0
console.log(buf.lastIndexOf('buffer'));
// Prints: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// Prints: 17
console.log(buf.lastIndexOf(97));
// Prints: 15 (97 is the decimal ASCII value for 'a')
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// Prints: -1
console.log(buf.lastIndexOf('buffer', 5));
// Prints: 5
console.log(buf.lastIndexOf('buffer', 4));
// Prints: -1

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// Prints: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// Prints: 4const { Buffer } = require('node:buffer');

const buf = Buffer.from('this buffer is a buffer');

console.log(buf.lastIndexOf('this'));
// Prints: 0
console.log(buf.lastIndexOf('buffer'));
// Prints: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// Prints: 17
console.log(buf.lastIndexOf(97));
// Prints: 15 (97 is the decimal ASCII value for 'a')
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// Prints: -1
console.log(buf.lastIndexOf('buffer', 5));
// Prints: 5
console.log(buf.lastIndexOf('buffer', 4));
// Prints: -1

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// Prints: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// Prints: 4

If value is not a string, number, or Buffer, this method will throw a TypeError. If value is a number, it will be coerced to a valid byte value, an integer between 0 and 255.

If byteOffset is not a number, it will be coerced to a number. Any arguments that coerce to NaN, like {} or undefined, will search the whole buffer. This behavior matches String.prototype.lastIndexOf().

import { Buffer } from 'node:buffer';

const b = Buffer.from('abcdef');

// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));

// Passing a byteOffset that coerces to NaN.
// Prints: 1, searching the whole buffer.
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));

// Passing a byteOffset that coerces to 0.
// Prints: -1, equivalent to passing 0.
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));const { Buffer } = require('node:buffer');

const b = Buffer.from('abcdef');

// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));

// Passing a byteOffset that coerces to NaN.
// Prints: 1, searching the whole buffer.
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));

// Passing a byteOffset that coerces to 0.
// Prints: -1, equivalent to passing 0.
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));

If value is an empty string or empty Buffer, byteOffset will be returned.