Javascript 在 JSON 对象的顶部添加一些东西
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Adding something to the top of a JSON object
提问by Click Upvote
I have a JSON object which is initiated when the page is loaded, like this:
我有一个 JSON 对象，它在页面加载时启动，如下所示：
data[foo] = bar;
data[foo2] = bar2;
data[foo3] = bar3;
Is there a way to inject an element before the first fooelement, so that when doing a for var i in data, the new element will be looped through before the elements that were added when the object was initiated?
有没有办法在第一个元素之前注入一个元素foo，以便在执行 a 时for var i in data，新元素将在对象启动时添加的元素之前循环？
The reason is, I'm displaying some items to the user. When the user adds a new item via javascript, I want this new item to be displayed above all the existing items, however when I add the new item, i.e
原因是，我正在向用户显示一些项目。当用户通过 javascript 添加新项目时，我希望这个新项目显示在所有现有项目的上方，但是当我添加新项目时，即
data[newItem] = newItem;
Then the JSON object looks like this:
然后 JSON 对象如下所示：
data[foo] = bar;
data[foo2] = bar2;
data[foo3] = bar3;
data[newItem] = newItem;
Instead of how I want, which is:
而不是我想要的方式，即：
data[newItem] = newItem;
data[foo] = bar;
data[foo2] = bar2;
data[foo3] = bar3;
Any ideas?
有任何想法吗？
回答by Joseph
In JS, object properties' order is not guaranteed. Therefore, even if they are ordered in the JSON string, when parsed as a JS object, you will never predict in what order they come up.
在 JS 中，不保证对象属性的顺序。因此，即使它们在 JSON 字符串中排序，当解析为 JS 对象时，您也永远无法预测它们以什么顺序出现。
Better use arrays instead. You could use the unshift()method to put the item in the first index.
最好使用数组代替。您可以使用该unshift()方法将项目放在第一个索引中。
var data = [bar,bar2,bar3];
data.unshift(newItem);
//data = [newItem,bar,bar2,bar3];
回答by Click Upvote
As a compliment to Joseph the Dreamer's answer, I have ran some quick checks in firefox & chrome.
作为一种恭维约瑟夫·梦想家的答案，我已经跑在Firefox和Chrome的一些快速检查。
Firefox:
火狐：
var obj = {};
obj.a = 'a';
obj.c = 'c';
obj.b = 'b';
obj['0'] = '0';
for(var i in obj){
console.log(i);
}
//prints:
a
c
b
0
Chrome:
铬合金：
var obj = {};
obj.a = 'a';
obj.c = 'c';
obj.b = 'b';
obj['0'] = '0';
for(var i in obj){
console.log(i);
}
//prints:
0
a
c
b
回答by raubas
I've stumbled upon this and achieved it using:
我偶然发现了这一点并使用以下方法实现了它：
const newObject = Object.assign({first: value}, oldObject)
const newObject = Object.assign({first: value}, oldObject)
As mentioned, order is not guaranteed but for me this is good enough. :)
如前所述，订单不能保证，但对我来说这已经足够了。:)
回答by Incognito
Is there a way to inject an element before the first foo element?
有没有办法在第一个 foo 元素之前注入一个元素？
Which comes first in the array:
哪个是数组中的第一个：
window.object or window.alert?
window.object 或 window.alert？
Neither, objects don't have an order. If you want an array use an array. Objects are not arrays.
两者都没有，对象没有顺序。如果你想要一个数组，请使用一个数组。对象不是数组。
If you want
如果你想
var ThingsInOrder = [
FirstThing,
SecondThing,
ThirdThing
];
ThingsInOrder.push(ForthThing);
Use an array.
使用数组。
If you want:
如果你想：
var ThingsNeverInOrder = {
Window,
Alert,
Derp,
Herp
};
ThingsNeverInOrder.foo = bar;
Use an object.
使用一个对象。
回答by virender nehra
Instead of adding new value in the same object, you can create a new object and arrange properties order as you want. example :
您可以创建一个新对象并根据需要排列属性顺序，而不是在同一对象中添加新值。例子 ：
var objj1 = {name:'viru',lastname:'nehra'};
So create a new object with new property which you want on top:
因此，创建一个具有您想要的新属性的新对象：
var obj2 = {age: 21}
and the run:
和运行：
for(var key in objj1){
obj2[key] = objj1[key]
}
obj2 = {age: 21, name: "viru", lastname: "nehra"}
回答by Samir Adel
I think you can convert it to string, append your data at the beginning of the string then re-convert the string to json using "eval"
我认为您可以将其转换为字符串，在字符串的开头附加您的数据，然后使用“eval”将字符串重新转换为 json
