删除对象属性是否像使用拼接删除数组元素一样？

Question

We have object type variable in Jquery:

var obj = *{"1234" : "xx", "4321" : "yy", "5555" : "hh", "2321" : "aa" };*

Lets say that I want to delete every property from property name "5555" to the end of the object(that means that I want to delete obj['5555'] and delete obj['2321'] ). I am interested in smartest way, trough loop, to do that.

In array I would use splice(2, arr.length) but I am confused.

Answer 1

There's no guarantee as to the order of an object's properties. When pasting your example object in my console, Here's what I saw:

> obj = {"1234" : "xx", "4321" : "yy", "5555" : "hh", "2321" : "aa" }
  Object {1234: "xx", 2321: "aa", 4321: "yy", 5555: "hh"}

As you can see, chrome ordered the properties in ascending order, like it would an array. Who knows, but maybe IE doesn't do this... Maybe some obscure browser would order the properties in descending order... There's no way of knowing what the actual object will look like, so perhaps have a rethink.
If all your properties are, essentially numeric, there's nothing wrong with using an array, in JS, the Array prototype is nothing but an augmented Object :

obj = [];
obj[1234] = 'xx';
obj[2321] = 'aa';
obj[5555] = 'hh';

The numeric indexes are coerced to strings internally anyway (because Array's are objects), so JS isn't going to create endless empty indexes for you, it resolves obj[200] just like it would resolve objectLiteral.undefinedProperty : scan instance, then prototypechain. If the requested property wasn't found, return undefined.

They're added as you go along, yet here are 2 ways:

//Assume simpel object (non-nested)
var newObj = JSON.parse(JSON.stringify(obj).replace(/\{|,\s*"5{4}"\s*:.+$/,'}'));

This, I think, is the easiest way, but not very reliable. The most "tried and tested" apprach is:

var unset = false;
for (var prop in obj)
{
    if (obj.hasOwnProperty(prop))
    {
        unset = unset || !!(prop === '5555');
        if (unset === true)
        {
            delete(obj[prop]);
        }
    }
}

The last approach creates an array, containing all keys, which you can iterate over, and delete the properties that way. It's here for completeness' sake only: I wouldn't use it, though, simply because it requires a browsers that supports the ES5 spec (not all browsers do, sadly), and there's no real advantage over the code above:

var keys = Object.keys(obj).sort(),//call sort to assure ascending order
toDelete = keys.splice(keys.indexOf('5555'), keys.length).sort();
for(var i=0;i<toDelete.length;i++)
{
    delete obj[toDelete[i]];
}

Answer 2

I would recommend you to get the index of the element from which you want to start deleting elements and then looping throw the object deleting the elements with a higher index.

You might want to create a function to make it more similar to splice i you prefer.

Answer 3

找到您要查找的元素，并将该特定元素及其后的任何元素设置为null 。

Answer 4

Push the obj to be searched and the value to be found into a function that returns a new object with only those properties up to the value you specified.

function returnNewobj(obj, value) {
  var newObj = {};
  for (var prop in obj) {
    if (obj.hasOwnProperty(prop)) {
      if (prop === value) return newObj;
      newObj[prop] = obj[prop];
    }
  }
  return newObj;
}

Edit: probably not necessary, but I added the hasOwnProperty line to be on the safe side.

Edit2: It's worth pointing out that new properties are added to objects in alphanumerical order, not to the end of objects like elements are added to arrays. So don't get caught out by that.

Answer 5

Its very tricky to delete property name however property value can be made null or undefined but removing property is difficult but you can do one thing can copy the required properties in new object its a workaround though here is a sample fiddle i use this often in this kind of situation

    objCopyTo[strToPropertyName] = objCopyFrom[strPropertyName];

here is the fiddle