fast-array-diff

fast-array-diff is a npm module to find the common or different parts of two array, it based on the solution of LCS (Longest common subsequence) problems, widely used in diff/patch of two arrays (like diff/patch feature in git).

The algorithm of this module is implemented based on the paper "An O(ND) Difference Algorithm and its Variations" by Eugene Myers, Algorithm Vol. 1 No. 2, 1986, pp. 251-266. The difference of this implementation to the implementation of npm module diff is: the space complexity of this implementation is O(N), while the implementation of diff is O(ND), so this implementation will cost less memory on large data set. Note: although the time complexity of the implementations are both O(ND), this implementation run slower than the diff.

Installation

You can install the module via npm:

npm install fast-array-diff

API

• same(arrayOld, arrayNew, compareFunc?) - Get the LCS of the two arrays.

  Return a list of the common subsequence. Like: [1,2,3]

  Note: The parameter compareFunc is optional, === will be used if no compare function supplied.

• diff(arrayOld, arrayNew, compareFunc?) - Get the difference the two array.

  Return an object of the difference. Like this:

{
    removed: [1,2,3],
    added: [2,3,4]
}

• getPatch(arrayOld, arrayNew, compareFunc?) - Get the patch array which transform from old array to the new.

  Return an array of edit action. Like this:

[
  { type: "remove", oldPos: 0, newPos: 0, items: [1] },
  { type: "add", oldPos: 3, newPos: 2, items: [4] },
];

• applyPatch(arrayOld, patchArray) - Thansform the old array to the new from the input patch array

  Return the new Array. The input value format can be same of return value of getPatch, and for the remove type, the items can be replaced to length value which is number.

[
  { type: "remove", oldPos: 0, newPos: 0, items: [1] },
  { type: "add", oldPos: 3, newPos: 2, items: [4] },
  { type: "remove", oldPos: 5, newPos: 3, length: 3 },
];

Examples

Example for same on array of number:

var diff = require("fast-array-diff");

console.log(diff.same([1, 2, 3, 4], [2, 1, 4]));
// Output: [2, 4]

Example for diff on array of Object with a compare function

function compare(personA, personB) {
  return (
    personA.firstName === personB.firstName &&
    personA.lastName === personB.lastName
  );
}

var result = diff.diff(
  [
    { firstName: "Foo", lastName: "Bar" },
    { firstName: "Apple", lastName: "Banana" },
    { firstName: "Foo", lastName: "Bar" },
  ],
  [
    { firstName: "Apple", lastName: "Banana" },
    { firstName: "Square", lastName: "Triangle" },
  ],
  compare
);

// Result is :
// {
//    removed:[
//        { firstName: 'Foo', lastName: 'Bar' },
//        { firstName: 'Foo', lastName: 'Bar' }
//    ],
//    added: [ { firstName: 'Square', lastName: 'Triangle' } ]
// }

Example for getPatch on array of number:

var es = diff.getPatch([1, 2, 3], [2, 3, 4]);

// Result is:
// [
//     { type: "remove", oldPos: 0, newPos: 0, items: [1] },
//     { type: "add", oldPos: 3, newPos: 2, items: [4] },
// ]

Example for applyPatch:

var arr = diff.applyPatch(
  [1, 2, 3],
  [
    { type: "remove", oldPos: 0, newPos: 0, length: 1 },
    { type: "add", oldPos: 3, newPos: 2, items: [4] },
  ]
);

// Result is:
// [2, 3, 4]

TypeScript

This module is written in TypeScript, you can import it directly in TypeScript and get the benefit of static type checking and auto-complete of IDE.

import * as diff from "fast-array-diff";

console.log(diff.same([1, 2, 3], [2, 3, 4]));

let result: diff.DiffData<number> = diff.diff([1, 2], [2, 3]);
// Note: DiffData is the interface of the difference result.

License

This module is licensed under MIT.

Changelog