How can you effectively find and represent the deep differences between two deeply nested JavaScript objects?

Finding the Differences Between Two Deeply Nested Objects

Problem: Calculate the deep differences between two deeply nested JavaScript objects, incorporating representation techniques to clearly identify changes.

Details: Given two objects, oldObj and newObj, a custom diff algorithm is needed to determine the differences between them, including changes in values, structure, and array order. The output should be represented in a clear and JSON-serializable manner.

Solution:

A custom class, deepDiffMapper, is designed to address this problem:

var deepDiffMapper = function () {
  return {

    // Constants representing change types
    VALUE_CREATED: 'created',
    VALUE_UPDATED: 'updated',
    VALUE_DELETED: 'deleted',
    VALUE_UNCHANGED: 'unchanged',

    map: function(obj1, obj2) {
      // Algorithm for comparing objects

      return diff;
    },
    
    compareValues: function (value1, value2) {
      // Logic for determining value changes
      
      return result;
    },

    // Helper functions to identify object types
    ...
  }
}();

Usage:

To use this class, simply call the map method with the two objects as arguments:

var result = deepDiffMapper.map(oldObj, newObj);

Output:

The map method returns an object representing the differences between the two input objects. The keys of this object correspond to the properties in newObj. Each value is itself an object with the following properties:

• type: The type of change (created, updated, deleted, or unchanged)
• data: The updated or new value (in case of a creation or update)

Example:

Given the following input objects:

var oldObj = {
  a: 'i am unchanged',
  b: 'i am deleted',
  e: {
    a: 1,
    b: false,
    c: null
  },
  f: [1, {
    a: 'same',
    b: [{
      a: 'same'
    }, {
      d: 'delete'
    }]
  }],
  g: new Date('2017.11.25')
};

var newObj = {
  a: 'i am unchanged',
  c: 'i am created',
  e: {
    a: '1',
    b: '',
    d: 'created'
  },
  f: [{
    a: 'same',
    b: [{
      a: 'same'
    }, {
      c: 'create'
    }]
  }, 1],
  g: new Date('2017.11.25')
};

The map method would return the following object representing the differences:

{
  b: {
    type: 'deleted',
    data: undefined
  },
  c: {
    type: 'created',
    data: 'i am created'
  },
  e: {
    a: {
      type: 'updated',
      data: '1'
    },
    b: {
      type: 'updated',
      data: ''
    },
    d: {
      type: 'created',
      data: 'created'
    }
  },
  f: {
    1: {
      type: 'deleted',
      data: undefined
    },
    2: {
      b: {
        1: {
          d: {
            type: 'deleted',
            data: undefined
          }
        },
        2: {
          c: {
            type: 'created',
            data: 'create'
          }
        }
      }
    }
  }
}

This representation clearly shows the changes made to the objects, highlighting created, updated, and deleted properties.

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