问题描述
限时送ChatGPT账号..我有两个数组,旧的和新的,它们在每个位置保存对象.我将如何同步或找到增量(即与旧数组相比,新数组中的新增内容、更新内容和删除内容)
I have two arrays, old and new, which hold objects at each position. How would I sync or find the delta (i.e. what is new, updated and deleted from the new array compared to the old array)
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"}
];
根据上面的数据,以id为key,我们会发现id=2的item有一个更新的title,id=3的item被删除了,id=4的item是new.
With the above data, using id as the key, we'd find that item with id=2 has an updated title, item with id=3 is deleted, and item with id=4 is new.
是否有现有的库具有有用的功能,或者是循环和内循环的情况,比较每一行..e.g.
Is there an existing library out there that has useful functions, or is it a case of loop and inner loop, compare each row..e.g.
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
}
}
这种比较三遍,找新的、更新的、删除的?
Do this kind of comparison three times, to find new, updated and deleted?
推荐答案
做你需要的事情没有什么神奇的.您需要遍历两个对象以查找更改.一个很好的建议是将您的结构转换为地图以加快搜索速度.
There's no magic to do what you need. You need to iterate through both objects looking for changes. A good suggestion is to turn your structure into maps for faster searches.
/**
* 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);
示例见http://jsfiddle/wjdZ6/1/
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