CODEWITHSUNDEEP
javascriptperformancehash
MaiaVictor
MaiaVictor

Reputation: 52957

In JavaScript, how do you find out the container object of a number field?

var obj = {a:1,b:2};
function parent_object(num){
    console.log('This number is inside the object ',<????>);
}
parent_object(obj.a)

This should output pointing to obj. The only way I found to do this is boxing every number object in an object which would keep a reference to the parent. This is, though, a performance killer. Is there a better way of keeping track of the location of a number?

Upvotes: 2

Views: 385

Answers (3)

Milad Naseri
Milad Naseri

Reputation: 4118

Actually no. And not only in JavaScript, but in none of the other conventional languages.

As far as I know, the only way would be for you to do exactly what you yourself said: boxing the number (or any other field type) in an object that would keep a reference (maybe by constructor injection) to its enclosing parent.

The boxing in question can be thus accomplished:

BoxedValue = function(value, parent) {
    this.value = value;
    this.parent = parent;
}

var i = {};
n.i = new BoxedValue(12, i)
console.log(i.n.parent);

However, generally speaking, the most important factor in your JavaScript application's performance for current browsers is the way you handle your memory usage. Therefore, this approach isn't really advisable, and I suggest you solve your problem, whatever it might be, via some other method.

Upvotes: 3

Draculater
Draculater

Reputation: 2278

var obj = {a:1,b:'string',c:2} 
for(prop in obj){
  if(typeof obj[prop]=='number'){
    console.log(prop + ' : ' + obj[prop] + ' found')
  }
}

logs:

a : 1 found

c : 2 found

Upvotes: 0

Platinum Azure
Platinum Azure

Reputation: 46183

There is no way to do this, because you can have objects reference each other from multiple places:

var num = 1;
var obj = {a: num, b: 2};
var obj2 = {x: num};

parent_object(obj.a);    // should it return obj or obj2? Both are technically correct!

What are you really trying to solve here? There is probably a better approach available to you.

Upvotes: 0

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