Created
May 23, 2012 14:19
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JavaScript implementation of set synchronisation. Bound by memory but minimizes database read writes.
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| var _ = require('underscore') | |
| , a = { | |
| 1: { id: '1', name: 'a' }, | |
| 2: { id: '2', name: 'b' }, | |
| 3: { id: '3', name: 'c' } | |
| } | |
| , b = { | |
| 2: { id: '2', name: 'b1' }, | |
| 3: { id: '3', name: 'c2' }, | |
| 4: { id: '4', name: 'd' } | |
| }; | |
| function getId(item) { | |
| return item.id; | |
| } | |
| function isDifferent(first, second) { | |
| return Object.keys(first).some(function(key) { | |
| return first[key] !== second[key]; | |
| }); | |
| } | |
| function create(newObject) { | |
| a[newObject.id] = newObject; | |
| } | |
| function update(id, newObject) { | |
| a[id] = newObject; | |
| } | |
| function del(id) { | |
| delete a[id]; | |
| } | |
| function sync(a, b, getId, isDifferent, create, update, del) { | |
| // Create sets | |
| var aIds = _.pluck(a, 'id') | |
| , bIds = _.pluck(b, 'id') | |
| , c = _.difference(aIds, bIds) | |
| , d = _.intersection(aIds, bIds) | |
| , e = _.difference(bIds, d); | |
| // Delete omitted items | |
| c.forEach(del); | |
| // Update only those that have changed | |
| d.forEach(function(index) { | |
| if (isDifferent(a[index], b[index])) { | |
| //update.push(b[index]); | |
| update(index, b[index]); | |
| } | |
| }); | |
| // Insert new items | |
| e.forEach(function(index) { | |
| create(b[index]); | |
| }); | |
| } | |
| sync(a, b, getId, isDifferent, create, update, del); | |
| console.log(a); |
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