@breautek/merge-change/test/custom-merge.spec.js

Simple library for deep merge of objects and other types (also for patch and immutable updates). Declarative operations to specific merge, for example to remove properties. Customize merging between specific types. Calculating diffs.

const mc = require('../index.js');

describe('Custom merge', () => {

  let lastOp;

  test('custom merge array', () => {
    lastOp = mc.addMerge('Array', 'Array', function(first, second, mode){
      // merge mode - create new array with deep clone
      if (mode === 'merge'){
        return first.concat(second).map(item => mc.merge(undefined, item));
      }
      // patch mode - mutate first array
      if (mode === 'patch'){
        first.splice(first.length, 0, ...second);
        return first;
      }
      // update mode - return first array if second is empty, or create new without clone
      if (second.length === 0){
        return first;
      } else {
        return first.concat(second);
      }
    });
    const obj1 = {a: 1, b: [1,2,3]};
    const obj2 = {a: 2, b: [3,4,5], c: 3};
    const result = mc.update(obj1, obj2);
    expect(result).toEqual({a:2, b: [1,2,3,3,4,5], c: 3});
  });

  test('default', () => {
    mc.addMerge('Array', 'Array', lastOp);
    const obj1 = {
      'a': 10,
      'b': {
        c: 1,
        d: [1, 2, 3],
        e: [{m: 1}, {m: 2}],
        i: [{_id: 1, _type: 'user'}, {_id: 2, _type: 'news'}]
      }
    };
    const obj2 = {
      'a': 2,
      'b': {
        d: [3, 4, 5],
        e: [{m: 2}, {m: 3}],
        i: [{_id: 1, prop: 'v1'}, {_id: 3, _type: 'news', prop: 'v2'}]
      },
      'n': 3
    };
    const result = mc.merge(obj1, obj2);

    expect(result).toEqual({
      'a': 2,
      'b': {
        c: 1,
        d: [/*1,2,*/3, 4, 5],
        e: [/*{m:1}, {m:2},*/ {m: 2}, {m: 3}],
        i: [{_id: 1, /*_type: 'user',*/ prop: 'v1'}, /*{_id: 2, _type: 'news'}, */{
          _id: 3,
          _type: 'news',
          prop: 'v2'
        }]
      },
      'n': 3
    });
  });

  test('not object with object', () => {
    const obj1 = null;
    const obj2 = {a: 1};
    const result = mc.merge(obj1, obj2);
    expect(result).toEqual({a:1});
  });


});