alexeiaccio / diff

diff

diff(left, right);

The diff function compares two objects and generates a difference report between them. It identifies added, removed, changed, nested, and unchanged properties, and returns an array of differences.

Parameters left (object): The left object to compare. right (object): The right object to compare. Return Value An array containing the differences between the left and right objects. Each difference is represented as an object with the following properties:

key (string): The key of the property that has a difference. old_value (any): The value of the property in the left object (null for added properties). new_value (any): The value of the property in the right object (null for removed properties). type (string): The type of difference. Possible values are "added", "removed", "changed", "nested", or "unchanged". children (array): An array of nested differences (present only for nested properties).

Example

const left = {
  name: "John",
  age: 30,
  address: {
    city: "New York",
    country: "USA",
  },
};

const right = {
  name: "John",
  age: 35,
  address: {
    city: "San Francisco",
    country: "USA",
  },
  email: "[e-mail]",
};

const differences = diff(left, right);
console.log(differences);

Output:

[
  {
    key: "age",
    old_value: 30,
    new_value: 35,
    type: "changed",
  },
  {
    key: "address",
    old_value: null,
    new_value: null,
    children: [
      {
        key: "city",
        old_value: "New York",
        new_value: "San Francisco",
        type: "changed",
      },
    ],
    type: "nested",
  },
  {
    key: "email",
    old_value: null,
    new_value: "[e-mail]",
    type: "added",
  },
];

In the above example, the diff function is used to compare two objects left and right. The resulting differences are logged to the console, indicating that the age property has changed, the address.city property has changed, and the email property has been added to the right object.

printDiff

printDiff(data);

The printDiff function takes a difference report between two objects and returns it as a formatted string.

Parameters data (Object): The input object to compare and generate the difference report. Return Value A formatted string representing the difference report.

Example

const obj1 = {
  a: 1,
  b: 2,
};

const obj2 = {
  a: 1,
  b: 3,
};

console.log(printDiff(obj1, obj2));

Output:

{
  - b: 2,
  + b: 3
}

In the above example, the printDiff function generates a difference report between obj1 and obj2. It detects that the value of the b property has changed from 2 to 3 and represents it as - b: 2 (removed) and + b: 3 (added).

How it Works

1. The printDiff function takes an input object data.
2. It initializes an empty array called result to store the lines of the difference report.
3. It pushes an opening curly brace { to the result array to start the report.
4. It calls the recursion function to generate the difference report recursively.
5. It pushes the lines of the difference report returned by the recursion function to the result array.
6. It pushes a closing curly brace } to the result array to end the report.
7. It joins the lines of the result array with newline characters \n and returns the formatted string.

For more details on how the difference report is generated, you can refer to the recursion function in the code snippet.