object-hash/readme.markdown

# object-hash

Generate hashes from objects and values in node and the browser.  Uses node.js
crypto module for hashing.  Supports SHA1 and many others (depending on the platform)
as well as custom streams (e.g. CRC32).

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[![NPM](https://nodei.co/npm-dl/object-hash.png?months=6&height=3)](https://www.npmjs.com/package/object-hash)

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* Hash values of any type.
* Supports a keys only option for grouping similar objects with different values.

```js
var hash = require('object-hash');

hash({foo: 'bar'}) // => '67b69634f9880a282c14a0f0cb7ba20cf5d677e9'
hash([1, 2, 2.718, 3.14159]) // => '136b9b88375971dff9f1af09d7356e3e04281951'
```

## Versioning Disclaimer

**IMPORTANT:** If you need lasting hash consistency, you should should lock `object-hash` at a specific version, because new versions (even patch versions) are likely to affect the result. For more info, see [this discussion](https://github.com/puleos/object-hash/issues/30).

## hash(value, options);
Generate a hash from any object or type.  Defaults to sha1 with hex encoding.
*  `algorithm` hash algo to be used: 'sha1', 'md5'. default: sha1
*  `excludeValues` {true|false} hash object keys, values ignored. default: false
*  `encoding` hash encoding, supports 'buffer', 'hex', 'binary', 'base64'. default: hex
*  `ignoreUnknown` {true|*false} ignore unknown object types. default: false
*  `replacer` optional function that replaces values before hashing. default: accept all values
*  `respectFunctionProperties` {true|false} Whether properties on functions are considered when hashing. default: true
*  `respectFunctionNames` {true|false} consider `name` property of functions for hashing. default: true
*  `respectType` {true|false} Whether special type attributes (`.prototype`, `.__proto__`, `.constructor`)
   are hashed. default: true
*  `unorderedArrays` {true|false} Sort all arrays using before hashing. Note that this affects *all* collections,
   i.e. including typed arrays, Sets, Maps, etc. default: false
*  `unorderedSets` {true|false} Sort `Set` and `Map` instances before hashing, i.e. make
   `hash(new Set([1, 2])) == hash(new Set([2, 1]))` return `true`. default: true

## hash.sha1(value);
Hash using the sha1 algorithm.

*Sugar method, equivalent to hash(value, {algorithm: 'sha1'})*

## hash.keys(value);
Hash object keys using the sha1 algorithm, values ignored.

*Sugar method, equivalent to hash(value, {excludeValues: true})*

## hash.MD5(value);
Hash using the md5 algorithm.

*Sugar method, equivalent to hash(value, {algorithm: 'md5'})*

## hash.keysMD5(value);
Hash object keys using the md5 algorithm, values ignored.

*Sugar method, equivalent to hash(value, {algorithm: 'md5', excludeValues: true})*

## hash.writeToStream(value, [options,] stream):
Write the information that would otherwise have been hashed to a stream, e.g.:
```js
hash.writeToStream({foo: 'bar', a: 42}, {respectType: false}, process.stdout)
// => e.g. 'object:a:number:42foo:string:bar'
```

## Installation

node:
```js
npm install object-hash
```

browser: */dist/object_hash.js*
```
<script src="object_hash.js" type="text/javascript"></script>

<script>
  var hash = objectHash.sha1({foo:'bar'}); 
  
  console.log(hash); // e003c89cdf35cdf46d8239b4692436364b7259f9
</script>
```

## Example usage
```js
var hash = require('object-hash');

var peter = {name: 'Peter', stapler: false, friends: ['Joanna', 'Michael', 'Samir'] };
var michael = {name: 'Michael', stapler: false, friends: ['Peter', 'Samir'] };
var bob = {name: 'Bob', stapler: true, friends: [] };

/***
 * sha1 hex encoding (default)
 */
hash(peter);
// 14fa461bf4b98155e82adc86532938553b4d33a9
hash(michael);
// 4b2b30e27699979ce46714253bc2213010db039c
hash(bob);
// 38d96106bc8ef3d8bd369b99bb6972702c9826d5

/***
 * hash object keys, values ignored
 */
hash(peter, { excludeValues: true });
// 48f370a772c7496f6c9d2e6d92e920c87dd00a5c
hash(michael, { excludeValues: true });
// 48f370a772c7496f6c9d2e6d92e920c87dd00a5c
hash.keys(bob);
// 48f370a772c7496f6c9d2e6d92e920c87dd00a5c

/***
 * md5 base64 encoding
 */
hash(peter, { algorithm: 'md5', encoding: 'base64' });
// 6rkWaaDiG3NynWw4svGH7g==
hash(michael, { algorithm: 'md5', encoding: 'base64' });
// djXaWpuWVJeOF8Sb6SFFNg==
hash(bob, { algorithm: 'md5', encoding: 'base64' });
// lFzkw/IJ8/12jZI0rQeS3w==
```

## Legacy Browser Support
IE <= 8 and Opera <= 11 support dropped in version 0.3.0.  If you require 
legacy browser support you must either use an ES5 shim or use version 0.2.5
of this module.

## Development

```
git clone https://github.com/puleos/object-hash
```

### gulp tasks
* `gulp watch` (default) watch files, test and lint on change/add
* `gulp test` unit tests
* `gulp karma` browser unit tests
* `gulp lint` jshint
* `gulp dist` create browser version in /dist

## License
MIT