A simple JavaScript synchronisation module for Node.JS. Used to keep two sets of data which have a unique key in sync whilst keeping data writes to a minimum.

npm install data-sync

var dataSync = require('data-sync')()

dataSync.sync(
  dataSync.formatArray('id', originalData)
  dataSync.formatArray('id', newData),
  'id',
  isDifferent,
  create,
  update,
  del,
  function(error) {
    console.log('Data Sync Complete')
  }
)

For a complete example please refer to the included unit test.

The data-sync module contains two functions. These are:

formatArray(uniqueId, dataArray)
sync(originalDataHash, newDataHash, uniqueId, comparatorFunction, createFunction, updateFunction, deleteFunction, finalCallback)

formatArray is used to convert an array of data into the correct format required to perform the data sync. It takes two parameters. These are as follows:

1. unqiueId: The name of the key which is to be used as a unique ID for each object.
2. dataArray: The array of data.

e.g input

formatArray(
  'id',
  [
    {id: 1, name: 'Fred'},
    {id: 2, name: 'Jim'},
    {id: 3, name: 'Tom'}
  ]
)

e.g output

{
  1: {id: 1, name: 'Fred'},
  2: {id: 2, name: 'Jim'},
  3: {id: 3, name: 'Tom'}
}

sync is used to perform the actual data syncronisation. It takes 8 parameters. These are as follows:

1. originalDataHash: Original data in the format produced by calling formatArray().
2. newDataHash: New data in the format produced by calling formatArray().
3. uniqueId: Name of the key which is to be used as a unique ID for each object.
4. comparatorFunction: Used to determine if two objects should be considered different and therefore call update(). Should return true if there is a difference. Parameters are: oldObject, newObject.
5. createFunction Function called when an object is present within the new data which is not in the original. Parameters are newObject, callback.
6. updateFunction Function called when an object has changed within the new data. Parameters are uniqueIdValue, oldObject, newObject, callback.
7. deleteFunction Function called when an object is present within the original data, but not the new data. Parameters are uniqueIdValue, oldObject, callback.
8. finalCallback Function called when data syncronisation is complete.

e.g

Given the following:

var originalData = [
      {id: 1, name: 'Fred'},
      {id: 2, name: 'Jim'},
      {id: 3, name: 'Tom'}
    ]
  , newData = [
      {id: 1, name: 'Fred'},
      {id: 3, name: 'Barney'},
      {id: 4, name: 'Dave'}
    ];

You would expect the output from calling sync() to be:

originalData = [
  {id: 1, name: 'Fred'},
  {id: 3, name: 'Barney'},
  {id: 4, name: 'Dave'}
];

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Paul Serby

Licenced under the New BSD License