Object Difference

This library provide a function to get deep difference between two javascript objects.

It's main focus is to highlight differences between two objects, before and after saving to a database, to administer a database change log.

This project is a fork of yyk222/object-difference-js. This version changes the project in a few ways for the City's use case.

• Converts the project to Typescript.
• Updates the code with more current Javascript functionality.
• Simplifies the comparisons for our use case.

Installation

npm install @cityssm/object-difference

Usage

import getObjectDifference from '@cityssm/object-difference'

const personBefore = {
  firstName: 'John',
  age: 30,
  gender: 'm',
  address: {
    city: 'New York',
    country: 'USA'
  }
}

const personAfter = {
  firstName: 'John',
  lastName: 'Doe',
  age: 31,
  address: {
    city: 'Los Angeles',
    country: 'USA'
  }
}

const differences = getObjectDifference(personBefore, personAfter)

console.log(differences)

/*
  [
    { property: 'age', type: 'updated', from: 30, to: 31 },
    { property: 'gender', type: 'deleted', from: 'm', to: undefined },
    {
      property: 'address.city',
      type: 'updated',
      from: 'New York',
      to: 'Los Angeles'
    },
    { property: 'lastName', type: 'created', from: undefined, to: 'Doe' }
  ]
 */

Property names are chained by "." between levels. Type can have 4 values:

• updated - Property is present in both objects, but changed.
• created - Property is blank in the first object, and present in the second.
• deleted - Property is present in the first object, and blank in the second.
• NA - Properties cannot be compared (i.e. functions)

Comparison Rules

First types are checked. Unlike the project this is based off, strings and numbers are not considered the same, and a change in type will be flagged as a difference.

Next, simple values are compared (i.e. boolean, number, and string).

Next, Date objects are compared using the getTime() function.

Finally, arrays are compared. Order does not matter, just the elements.

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A completely free, open source, web-based application to assist cemetery managers with managing their cemetery records.