object diff javascript code example

Example: object diff javascript

// const { inspect } = require('util')
const { transform, isEqual, isArray, isObject } = require('lodash')

/**
 * Find difference between two objects
 * https://davidwells.io/snippets/get-difference-between-two-objects-javascript
 *
 * @param  {object} origObj - Source object to compare newObj against
 * @param  {object} newObj  - New object with potential changes
 * @return {object} differences
 */
function difference(origObj, newObj) {
  function changes(newObj, origObj) {
    let arrayIndexCounter = 0
    return transform(newObj, function (result, value, key) {
      if (!isEqual(value, origObj[key])) {
        let resultKey = isArray(origObj) ? arrayIndexCounter++ : key
        result[resultKey] =
          isObject(value) && isObject(origObj[key])
            ? changes(value, origObj[key])
            : value
      }
    })
  }
  return changes(newObj, origObj)
}

/* Usage */

const originalObject = {
  foo: 'bar',
  baz: 'fizz',
  cool: true,
  what: {
    one: 'one',
    two: 'two'
  },
  wow: {
    deep: {
      key: ['a', 'b', 'c'],
      values: '123'
    }
  },
  array: ['lol', 'hi', 'there']
}

const newObject = {
  foo: 'bar',
  baz: 'fizz',
  cool: false, // <-- diff
  what: {
    one: 'one',
    two: 'twox' // <-- diff
  },
  wow: {
    deep: {
      key: ['x', 'y', 'c'], // <-- diff
      values: '098' // <-- diff
    }
  },
  array: ['lol', 'hi', 'difference'] // <-- diff
}

// Get the Diff!
const diff = difference(originalObject, newObject)

console.log(inspect(diff, {showHidden: false, depth: null, colors: true}))

// result:
// {
//   cool: false,
//   what: { two: 'twox' },
//   wow: { deep: { key: [ 'x', 'y' ], values: '098' } },
//   array: [ 'difference' ]
// }


if (diff.cool) {
  console.log('Coolness changed to', diff.cool)
}