|
| 1 | +'use strict'; |
| 2 | + |
| 3 | +function arrayEquals(before, after) { |
| 4 | + if(before.length !== after.length) { |
| 5 | + return false; |
| 6 | + } |
| 7 | + for(var i=0; i<before.length; i++) { |
| 8 | + if(after[i] !== before[i]) { |
| 9 | + return false; |
| 10 | + } |
| 11 | + } |
| 12 | + return true; |
| 13 | +} |
| 14 | + |
| 15 | +module.exports = function generate(before, after) { |
| 16 | + if(before === null || after === null || |
| 17 | + typeof before !== 'object' || typeof after !== 'object' || |
| 18 | + Array.isArray(before) !== Array.isArray(after)) { |
| 19 | + return after; |
| 20 | + } |
| 21 | + |
| 22 | + if(Array.isArray(before)) { |
| 23 | + if(!arrayEquals(before, after)) { |
| 24 | + return after; |
| 25 | + } |
| 26 | + return undefined; |
| 27 | + } |
| 28 | + |
| 29 | + var patch = {}; |
| 30 | + var beforeKeys = Object.keys(before); |
| 31 | + var afterKeys = Object.keys(after); |
| 32 | + |
| 33 | + // removed elements |
| 34 | + beforeKeys.filter(function(key) { |
| 35 | + return afterKeys.indexOf(key) === -1; |
| 36 | + }) |
| 37 | + .forEach(function(key) { |
| 38 | + patch[key] = null; |
| 39 | + }); |
| 40 | + |
| 41 | + // new elements |
| 42 | + afterKeys.filter(function(key) { |
| 43 | + return beforeKeys.indexOf(key) === -1; |
| 44 | + }) |
| 45 | + .forEach(function(key) { |
| 46 | + patch[key] = after[key]; |
| 47 | + }); |
| 48 | + |
| 49 | + // modified elements |
| 50 | + beforeKeys.filter(function(i) { |
| 51 | + return afterKeys.indexOf(i) !== -1; |
| 52 | + }) |
| 53 | + .forEach(function(key) { |
| 54 | + if(before[key] !== null && typeof before[key] === 'object') { |
| 55 | + var subPatch = generate(before[key], after[key]); |
| 56 | + if(subPatch !== undefined) { |
| 57 | + patch[key] = subPatch; |
| 58 | + } |
| 59 | + } else if(before[key] !== after[key]) { |
| 60 | + patch[key] = after[key]; |
| 61 | + } |
| 62 | + }); |
| 63 | + return (Object.keys(patch).length > 0 ? patch : undefined); |
| 64 | +}; |
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