newxps/var-diff

javascript variable diff algorithm

var-diff

get the difference between two variables

Compatibility

IE	Chrome	Firefox	Opera	Safari
✔️	✔️	✔️	✔️	✔️

Installation

npm i var-diff

or

<script src="var-diff.js"></script>

Usage

use var patches = diff.get(origin, target, [key]) to get difference patches between origin and target variables.

key is an optional parameter used to improve sorting performance. patches is an array containing all of the differences betwen two variables

// patches
t: type   1-create 2-delete 3-edit 4-replace
p: path {Array}
v: value
i: new index(when type is replace)

use diff.apply(origin, patches) to make the origin variable apply the patches then become the target varible. but all references of the origin variable are reserved.

const diff = require('var-diff');

let a = [1, 2, 3, {id: 1, name: 'tom'}, {id: 2, name: 'jack'}]
let b = [2, {id: 2, name: 'will'}, 3, {id: 1, name: 'lucy'}]

let patches = diff.get(origin, target, 'id');
console.log(patches);

/**
 * patches
[ 
  { t: 2, p: [ 0 ] },                       // remove the 0th element 
  { t: 3, p: [ 2, 'name' ], v: 'lucy' },    // update the name of the 2th element to 'lucy'
  { t: 3, p: [ 3, 'name' ], v: 'will' },    // update the name of the 3th element to 'will'
  { t: 4, p: [ 3 ], i: 1 },                 // change the 3th element to the 1th position
  { t: 4, p: [ 3 ], i: 2 }                  // change the 3th element to the 2th position
]
 */


a = diff.apply(a, patches);

console.log(JSON.stringify(a) === JSON.stringify(b));

// true

Examples

var a = {
  name: 'tom',
  gender: 'male',
  list: [{
    id: 1,
    label: 'teacher'
  }]
}

var b = {
  name: 'jack',
  list: [{
    id: 2,
    label: 'worker'
  }, {
    id: 3,
    label: 'student'
  }, {
    id: 1,
    label: ''
  }]
}

p = diff.get(a, b, 'id');

console.log(p);
/**
  t: type   1-create 2-delete 3-edit 4-replace
  p: path {Array}
  v: value
  i: new index(when type is replace)

 [{ t: 3, p: [ 'name' ], v: 'jack' },
  { t: 2, p: [ 'gender' ] },
  { t: 3, p: [ 'list', 0, 'label' ], v: '' },
  { t: 1, p: [ 'list', 1 ], v: { id: 2, label: 'worker' } },
  { t: 1, p: [ 'list', 2 ], v: { id: 3, label: 'student' } },
  { t: 4, p: [ 'list', 0 ], i: 2 },
  { t: 4, p: [ 'list', 1 ], i: 0 },
  { t: 1, p: [ 'age' ], v: 25 }]
 */

var aa = diff.apply(a, p, 'id'); // key
console.log(JSON.stringify(aa) === JSON.stringify(b));  // true

var a = [NaN, NaN];
var b = [NaN, NaN];

var p = diff.get(a, b, 'id');

console.log(p); // []

LICENSE

MIT