在javascript中移动对象元素位置

Question

I'm trying to find a way to move an object element to a specific position.

For example, I've this object :

{
    "element1" : {} // object,
    "element2" : {},
    "element3" : {}
}

And I search to move element3 at the first position :

{
    "element3" : {},
    "element1" : {},
    "element2" : {}
}

Thanks for your help !

Answer 1

JavaScript objects don't have ordering. You should use an array of objects instead.

var arr = [
  { id: 'element1' },
  { id: 'element2' },
  { id: 'element3' }
]

You could then reorder it something like:

var first = arr.splice(0, 1);
arr.push(first);

Maybe you could then grab specific elements based on id:

var out = arr.filter(function (el) {
  return el.id === 'element1';
});

Answer 2

Objects in JavaScript are essentially hash maps. Their properties don't have any ordering, per se. They are simply name value pairs.

You are probably confusing objects with arrays, in which case ordering does indeed matter.

Answer 3

Here's my code for doing that logic. Thanks!

function _moveElementObject(object, from, to) {
    var newObjects = [];
    var newObject = {};
    var oldObject = {};
    var firstObject = {};
    var lastObject = {};
    var toMoveKey = "";
    var toMoveValue;
    oldObject = object;
    var objLength = _countProperties(oldObject);
    var keyNo = 1;
    for (var key in oldObject) {
        if (keyNo == from) {
            toMoveKey = key;
            toMoveValue = oldObject[key];
        }
        keyNo++;
    }
    console.log(oldObject);

    keyNo = 1;
    for (var key in oldObject) {
        if (keyNo < to) {
            firstObject[key] = oldObject[key];
            newObject[key] = firstObject[key];
        }
        keyNo++;
    }
    console.log(firstObject);

    keyNo = 1;
    for (var key in oldObject) {
        if (to <= objLength) {
            lastObject[key] = oldObject[key];
        }
        keyNo++;
    }
    delete lastObject[toMoveKey];
    newObject[toMoveKey] = toMoveValue;

    for (var key in lastObject) {
        newObject[key] = lastObject[key];
    }
    console.log(newObject);
    console.log("push");
    return newObject;
}

var sampleObj = {
    "element1" : {} // object,
    "element2" : {},
    "element3" : {}
};

_moveElementObject(sampleObj,3,1);

// output object,
{
    "element3" : {},
    "element1" : {}, 
    "element2" : {},
}