JavaScript同步兩個數組（對象）/查找增量

Question

我有兩個數組，舊的和新的，它們在每個位置都有對象。我將如何同步或找到增量（即什麼是新的，更新和新的陣列中刪除較舊的陣列）

var o = [ 
    {id:1, title:"title 1", type:"foo"}, 
    {id:2, title:"title 2", type:"foo"}, 
    {id:3, title:"title 3", type:"foo"} 
]; 

var n = [ 
    {id:1, title:"title 1", type:"foo"}, 
    {id:2, title:"title updated", type:"foo"}, 
    {id:4, title:"title 4", type:"foo"} 
]; 

通過上述數據，使用ID作爲關鍵，我們會發現， id = 2的項目有更新的標題，id = 3的項目被刪除，id = 4的項目是新的。

是否有一個現有的庫，有有用的功能，或者它是一個循環和內部循環的情況下，比較每一行..例如。

for(var i=0, l=o.length; i<l; i++) 
{ 
    for(var x=0, ln=n.length; x<ln; x++) 
    { 
     //compare when o[i].id == n[x].id  
    } 
} 

做這種比較三次，找到新的，更新和刪除？

Answer 1

沒有什麼魔法可以滿足您的需求。您需要遍歷這兩個對象以查找更改。一個好的建議是把你的結構變成地圖以加快搜索速度。

/** 
* Creates a map out of an array be choosing what property to key by 
* @param {object[]} array Array that will be converted into a map 
* @param {string} prop Name of property to key by 
* @return {object} The mapped array. Example: 
*  mapFromArray([{a:1,b:2}, {a:3,b:4}], 'a') 
*  returns {1: {a:1,b:2}, 3: {a:3,b:4}} 
*/ 
function mapFromArray(array, prop) { 
    var map = {}; 
    for (var i=0; i < array.length; i++) { 
     map[ array[i][prop] ] = array[i]; 
    } 
    return map; 
} 

function isEqual(a, b) { 
    return a.title === b.title && a.type === b.type; 
} 

/** 
* @param {object[]} o old array of objects 
* @param {object[]} n new array of objects 
* @param {object} An object with changes 
*/ 
function getDelta(o, n, comparator) { 
    var delta = { 
     added: [], 
     deleted: [], 
     changed: [] 
    }; 
    var mapO = mapFromArray(o, 'id'); 
    var mapN = mapFromArray(n, 'id');  
    for (var id in mapO) { 
     if (!mapN.hasOwnProperty(id)) { 
      delta.deleted.push(mapO[id]); 
     } else if (!comparator(mapN[id], mapO[id])){ 
      delta.changed.push(mapN[id]); 
     } 
    } 

    for (var id in mapN) { 
     if (!mapO.hasOwnProperty(id)) { 
      delta.added.push(mapN[id]) 
     } 
    } 
    return delta; 
} 

// Call it like 
var delta = getDelta(o,n, isEqual); 

爲例

Answer 2

見http://jsfiddle.net/wjdZ6/1/這是@Juan Mendes答案的打字稿版本

mapFromArray(array: Array<any>, prop: string): { [index: number]: any } { 
    const map = {}; 
    for (let i = 0; i < array.length; i++) { 
     map[array[i][prop]] = array[i]; 
    } 
    return map; 
    } 

    isEqual(a, b): boolean { 
    return a.title === b.title && a.type === b.type; 
    } 

    getDelta(o: Array<any>, n: Array<any>, comparator: (a, b) => boolean): { added: Array<any>, deleted: Array<any>, changed: Array<any> } { 
    const delta = { 
     added: [], 
     deleted: [], 
     changed: [] 
    }; 
    const mapO = this.mapFromArray(o, 'id'); 
    const mapN = this.mapFromArray(n, 'id'); 
    for (const id in mapO) { 
     if (!mapN.hasOwnProperty(id)) { 
     delta.deleted.push(mapO[id]); 
     } else if (!comparator(mapN[id], mapO[id])) { 
     delta.changed.push(mapN[id]); 
     } 
    } 

    for (const id in mapN) { 
     if (!mapO.hasOwnProperty(id)) { 
     delta.added.push(mapN[id]); 
     } 
    } 
    return delta; 
    }