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doc: clarify Buffer.indexOf/lastIndexOf edge cases · nodejs/node@21a94ab · GitHub

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doc: clarify Buffer.indexOf/lastIndexOf edge cases
PR-URL: #10162 Fixes: #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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‎doc/api/buffer.md‎

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@@ -1156,6 +1156,30 @@ console.log(utf16Buffer.indexOf('\u03a3', 0, 'ucs2'));
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console.log(utf16Buffer.indexOf('\u03a3', -4, 'ucs2'));
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```
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If `value` is not a string, number, or `Buffer`, this method will throw a
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`TypeError`. If `value` is a number, it will be coerced to a valid byte value,
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an integer between 0 and 255.
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If `byteOffset` is not a number, it will be coerced to a number. Any arguments
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that coerce to `NaN` or 0, like `{}`, `[]`, `null` or `undefined`, will search
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the whole buffer. This behavior matches [`String#indexOf()`].
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```js
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const b = Buffer.from('abcdef');
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// Passing a value that's a number, but not a valid byte
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// Prints: 2, equivalent to searching for 99 or 'c'
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console.log(b.indexOf(99.9));
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console.log(b.indexOf(256 + 99));
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// Passing a byteOffset that coerces to NaN or 0
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// Prints: 1, searching the whole buffer
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console.log(b.indexOf('b', undefined));
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console.log(b.indexOf('b', {}));
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console.log(b.indexOf('b', null));
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console.log(b.indexOf('b', []));
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```
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### buf.includes(value[, byteOffset][, encoding])
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<!-- YAML
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added: v5.3.0
@@ -1276,6 +1300,33 @@ console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'ucs2'));
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console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'ucs2'));
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```
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If `value` is not a string, number, or `Buffer`, this method will throw a
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`TypeError`. If `value` is a number, it will be coerced to a valid byte value,
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an integer between 0 and 255.
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If `byteOffset` is not a number, it will be coerced to a number. Any arguments
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that coerce to `NaN`, like `{}` or `undefined`, will search the whole buffer.
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This behavior matches [`String#lastIndexOf()`].
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```js
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const b = Buffer.from('abcdef');
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// Passing a value that's a number, but not a valid byte
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// Prints: 2, equivalent to searching for 99 or 'c'
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console.log(b.lastIndexOf(99.9));
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console.log(b.lastIndexOf(256 + 99));
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// Passing a byteOffset that coerces to NaN
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// Prints: 1, searching the whole buffer
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console.log(b.lastIndexOf('b', undefined));
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console.log(b.lastIndexOf('b', {}));
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// Passing a byteOffset that coerces to 0
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// Prints: -1, equivalent to passing 0
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console.log(b.lastIndexOf('b', null));
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console.log(b.lastIndexOf('b', []));
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```
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### buf.length
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<!-- YAML
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added: v0.1.90
@@ -2413,6 +2464,8 @@ console.log(buf);
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[RFC1345]: https://tools.ietf.org/html/rfc1345
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[RFC4648, Section 5]: https://tools.ietf.org/html/rfc4648#section-5
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[`String.prototype.length`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length
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[`String#indexOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf
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[`String#lastIndexOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf
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[`TypedArray`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
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[`TypedArray.from()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from
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[`Uint32Array`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array

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