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doc: clarify Buffer.indexOf/lastIndexOf edge cases

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PR-URL: https://github.com/nodejs/node/pull/10162
Fixes: https://github.com/nodejs/node/issues/9801
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
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dcposch@dcpos.ch 2016-12-07 00:36:16 -08:00 committed by Roman Reiss
parent dd50cd9e4f
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doc/api/buffer.md
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@ -1164,6 +1164,30 @@ console.log(utf16Buffer.indexOf('\u03a3', 0, 'ucs2'));
console.log(utf16Buffer.indexOf('\u03a3', -4, 'ucs2'));
```
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` or 0, like `{}`, `[]`, `null` or `undefined`, will search
the whole buffer. This behavior matches [`String#indexOf()`].
```js
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.indexOf(99.9));
console.log(b.indexOf(256 + 99));
// Passing a byteOffset that coerces to NaN or 0
// Prints: 1, searching the whole buffer
console.log(b.indexOf('b', undefined));
console.log(b.indexOf('b', {}));
console.log(b.indexOf('b', null));
console.log(b.indexOf('b', []));
```
### buf.includes(value[, byteOffset][, encoding])
<!-- YAML
added: v5.3.0
@ -1284,6 +1308,33 @@ console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'ucs2'));
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'ucs2'));
```
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#lastIndexOf()`].
```js
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', []));
```
### buf.length
<!-- YAML
added: v0.1.90
@ -2463,6 +2514,8 @@ console.log(buf);
[RFC1345]: https://tools.ietf.org/html/rfc1345
[RFC4648, Section 5]: https://tools.ietf.org/html/rfc4648#section-5
[`String.prototype.length`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length
[`String#indexOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf
[`String#lastIndexOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf
[`TypedArray`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[`TypedArray.from()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from
[`Uint32Array`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array