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

• value <string> | <Buffer> | <Uint8Array> | <integer> 要搜索的内容。
• byteOffset <integer> 在 buf 中开始搜索的位置。如果为负数，则偏移量从 buf 的末尾计算。默认值： buf.length - 1。
• encoding <string> 如果 value 是一个字符串，则此编码用于确定将在 buf 中搜索的字符串的二进制表示。默认值： 'utf8'。
• 返回值：<integer> value 在 buf 中最后一次出现的索引，如果 buf 不包含 value，则返回 -1。

与 buf.indexOf() 相同，不同之处在于找到的是 value 的最后一次出现，而不是第一次出现。

【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拷贝

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

【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.】

如果 byteOffset 不是数字，它将被强制转换为数字。任何会被强制转换为 NaN 的参数，如 {} 或 undefined，将搜索整个缓冲区。此行为与 String.prototype.lastIndexOf() 相匹配。

【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', []));拷贝

如果 value 是空字符串或空的 Buffer，将返回 byteOffset。

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