hash-props

Get a hash of an object calculated from certain properties

Why?

This is useful for generating an id/key for an object to be used as the object's primary key in databases not supporting unique indexes/keys, e.g. RethinkDB.

Usage

Basic Module usage

const hashProps = require('hash-props');

const obj1 = {greeting: 'hello', to: 'world'};
const obj2 = {greeting: 'hello', to: 'universe'};

console.log(hashProps(obj1, ['greeting']));
// 5d41402abc4b2a76b9719d911017c592
console.log(hashProps(obj2, ['greeting']));
// 5d41402abc4b2a76b9719d911017c592

Generating id's to use in db's without unique keys

Some databases does not support unique keys/indexes, for instance RethinkDB.
By generating a hash id, based on the properties you want a unique key for, and using it as the object's primary key we can simulate the behavior of a unique key.

const {hashId} = require('hash-props');
const db = require('some-db-without-unique-keys');

const obj1 = {greeting: 'hello', to: 'world'}
db.insert(hashId(obj1, ['greeting']));
// inserts:
// { greeting: 'hello',
//  to: 'world',
//  id: '5d41402abc4b2a76b9719d911017c592' }
const obj2 = {greeting: 'hello', to: 'universe'};
db.insert(hashId(obj2, ['greeting']));
// does not insert the following, because of already existing primary key:
// { greeting: 'hello',
//  to: 'universe',
//  id: '5d41402abc4b2a76b9719d911017c592' }

API

hashProps(obj [, props])

| Name | Type | Description | |------|------|-------------| | obj | Object | The object to get a hash for | | props | Array<String> | The properties from obj to use for hash generation (optional) |

Returns: String an md5 hash based on given props property values in obj, if props is omitted a hash of the objects all properties will be generated.

hashId(obj [, props])

| Name | Type | Description | |------|------|-------------| | obj | Object | The object to generate a hash id for | | props | Array<String> | The properties from obj to use for hash generation (optional) |

Returns: Object, a clone of obj with an id property containing an md5 hash, generated by hashProps above.

hashStr(str)

| Name | Type | Description | |------|------|-------------| | str | String | A string to generate an md5 hash for |

Returns: String, the md5 hash for given str.

Installation

Install hash-props using npm:

npm install --save hash-props

License

MIT © Joakim Carlstein