Dynamically creating variables using the object key value pairs?

Question

Here is the code :

let box = {   
        aaa:111,
        bbb:222,
        ccc:333,
        destruct: function() { 
                   let des = ( {bbb} = box);
                   return des; 
                }
};
   

box.destruct();
aaa // return error : aaa is not defined
bbb // return 222

While i could use this syntax let {aaa,bbb,ccc} = box which is great. There would be a case in the future where another pair of keys and values would be added inside the object, for example ddd : 444, eee:555. Thus the coding in destruct : function()..... had to be updated too.

I would like to improve the object destructuring coding by using eval() and Object.keys().join(). This is the far i can go

        destruct : function() { 
                    let str = Object.keys( box ).join(); // "aaa,bbb,ccc"
                    let des = eval( "{" + str + "} = box" );
                    return des;
}

box.destruct() // return Unexpected token '='

what do you want from the `destruct` method - the values of all the keys of your `box` object? why not just use `Object.values(box)`? — iamaatoh, Jul 03 '20 at 14:19
This seems like a [XY-problem](http://xyproblem.info/) what are you trying to achieve? — 3limin4t0r, Jul 03 '20 at 14:35
I understand the ideia but I'm not sure if that would be nice because you wouldn't know the variable names for the object. — chriptus13, Jul 03 '20 at 14:36
hi @apple apple, let des = (**let** {bbb} = box) that let statement shouldn't be there. I've corrected it. Sorry — biskut nation, Jul 03 '20 at 16:11
@iamaatoh, the idea is to access functions (or any keys & value) inside the object without using Object.keys, Object.values, or dot / bracket notation. — biskut nation, Jul 03 '20 at 17:07

score 0 · Answer 1 · answered Jul 03 '20 at 14:45

0

So from the question, it seems like you are trying to dynamically create variables at run time using the object box key values, while you shouldn't be doing this. But if its the last option then you should do something like this below.

let box = {
  aaa: 111,
  bbb: 222,
  ccc: 333,
  destruct: function () {
    for (key in box) {
      eval(`${key} = ${box[key]}`);
    }
  },
};

box.destruct();

console.log(aaa, bbb, ccc);

answered Jul 03 '20 at 14:45

namar sood

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_"...while you shouldn't be doing this."_ why? is it because of the eval()? or the whole idea itself? – biskut nation Jul 03 '20 at 16:25
you can refer to this answer https://stackoverflow.com/questions/86513/why-is-using-the-javascript-eval-function-a-bad-idea , and also using this approach creates global variables which may override other important variables if not taken care of. – namar sood Jul 03 '20 at 16:33
Thanks! Will keep it my mind about the global variables. Maybe i will resort to fancy variable naming for time being. – biskut nation Jul 03 '20 at 16:55

score 0 · Accepted Answer · answered Jul 03 '20 at 15:34

Try setting the keys to window object

let box = {
  aaa: 111,
  bbb: 222,
  ccc: 333,
  destruct: function () {
    Object.assign(window, this, {destruct: undefined})
  },
};

box.destruct();

console.log(aaa, bbb, ccc);

let box = {
  aaa: 111,
  bbb: 222,
  ccc: 333,
  destruct: function () {
    for (key in this) {
      if (key == 'destruct') continue 
      window[key] = this[key]
    }
  },
};

box.destruct();

console.log(aaa, bbb, ccc);

Thanks! Never thought about assigning to window before. Seems neat too! — biskut nation, Jul 03 '20 at 16:23

Dynamically creating variables using the object key value pairs?

2 Answers2