javascript - 在两个 JavaScript 哈希中查找差异(添加和删除对)的最有效方法

Question

我有两个 JavaScript 字符串哈希值，对象称为“existingItems”和“newItems”。我想比较和提取哪些项目已添加(对于 newItems 是唯一的)和哪些已被删除(对于现有项目是唯一的)。我希望比较是在每对的关键上。

最有效的方法是什么？我应该先对元素进行分类吗？我应该提取数组的键并单独使用它们吗？

哈希值示例:

var existing = [];
existing.push(["456",{Ref:"456",Title:"ttt456",food:"soup"}]);
existing.push(["789",{Ref:"789",Title:"ttt789",color:"blue",duck:"sauce"}]);
existing.push(["abc",{Ref:"abc",Title:"tttabc",colour:"yellklow",duck:"sauce"}]);
existing.push(["xyz",{Ref:"xyz",Title:"tttabc",colour:"yellklow",duck:"sauce"}]);
existing.push(["123",{Ref:"123",Title:"ttt123",pet:"cat"}]);

var newits = [];
newits.push(["abc",{Ref:"abc",Title:"tttabc",food:"horse"}]);
newits.push(["456",{Ref:"456",Title:"ttt456",pet:"cat",color:"green",cat:"sauce"}]);
newits.push(["def",{Ref:"def",Title:"tttabc",noise:"moo"}]);


var itemsAdded = compareHash(existing,newits);
var itemsRemoved =compareHash(newits,existing); 

Answer 1

这些不是哈希值，而是数组! (在 Javascript 中，对象是哈希值)。

如果你像这样重写它们，可以更有效地完成:

var existing = {};
existing["456"] = {Ref:"456",Title:"ttt456",food:"soup"};
existing["789"] = {Ref:"789",Title:"ttt789",color:"blue",duck:"sauce"};
existing["abc"] = {Ref:"abc",Title:"tttabc",colour:"yellklow",duck:"sauce"};
existing["xyz"] = {Ref:"xyz",Title:"tttabc",colour:"yellklow",duck:"sauce"};
existing["123"] = {Ref:"123",Title:"ttt123",pet:"cat"};

var newits = {};
newits["abc"] = {Ref:"abc",Title:"tttabc",food:"horse"};
newits["456"] = {Ref:"456",Title:"ttt456",pet:"cat",color:"green",cat:"sauce"};
newits["def"] = {Ref:"def",Title:"tttabc",noise:"moo"};

var itemsAdded = compareHash(existing,newits);
var itemsRemoved =compareHash(newits,existing); 

现在您可以检查 newits 中是否存在“abc”，如下所示:

if (newits.hasOwnProperty('abc')) {
    // do what you need to do
}

循环访问对象中的属性(它们已经变成这样)——并回答您的问题:

function compareHash(oldObj, newObj) {
    var result = {};
    for (var key in newObj) {
        if (newObj.hasOwnProperty(key)) { // filter in case someone else has added properties to the global Object prototype
            if (!oldObj.hasOwnProperty(key)) {
                result[key] = newObj[key];
            }
        }
    }
    return result;
}