Defining a nested object property in Javascript

Question

I need to send a JSON object to a server which requires that the properties are nested. For example, the data object may be nested 2 levels deep. However, one cannot simply declare the object directly:

var foo = {};
foo.bar.bartwo = "data"; //Uncaught TypeError

I am currently attempting to bypass this by manually creating the nested object layer.

var foo = {};
foo.bar = {};
foo.bar.bartwo = "data"; //Successful

However, this can quickly get out of hand if the object requires multiple levels of nesting.

Is there a better method in Javascript or Jquery to handle this issue (which does not work by simply golfing the second code example)?

Clarification: The solution should be able to allow for direct access to nested properties, without necessitating that all of the intermediate properties also be created.

@naththedeveloper While your solution is more concise, it doesn't actually solve the root problem. The nesting may require multiple levels to be generated dynamically, which would not work with your example. — March Ho, Jun 22 '16 at 13:11
What you're asking is impossible because to add a property to an object, the object must exist. The best you can do is make a function that lessens the burden of doing so, like [this one](http://stackoverflow.com/a/11433067/5743988). — 4castle, Jun 22 '16 at 13:18

score 0 · Answer 1 · answered Jun 22 '16 at 13:22

0

without defining nested object i.e foo.bar = {}; you can not use or assign value to it javascript object must be defined first to use it otherwise it will give you 'undefined' error i.e foo.bar is undefined

answered Jun 22 '16 at 13:22

Akash

11
3

Yehuda Schwartz · Answer 2 · 2016-06-23T17:44:24.387

0

create a small method that does this

function nested(x, y){
nestedA="";
parts = x.split('.');
  for(i=0; i<parts.length; i++) {
    nestedA += parts[i];
    eval(nestedA + ' = {}');
    nestedA += '.';
}
eval(nestedA.slice(0,-1)+ '= "'+y+'"');
}
nested('foo.bar.bartwo', "data");

edited Jun 23 '16 at 17:44

answered Jun 22 '16 at 13:24

Yehuda Schwartz

3,378
3
29
38

Test your code. There are several syntax issues with it. – 4castle Jun 22 '16 at 13:27
What is `.=` doing? Is it concatenation? – 4castle Jun 22 '16 at 13:31
adding to the string – Yehuda Schwartz Jun 22 '16 at 13:32
Concatenation is JS would be `+=`, but then you're overwriting the value with `{}` anyway. Run your code please. – 4castle Jun 22 '16 at 13:33
thanks i missed that – Yehuda Schwartz Jun 22 '16 at 13:35
ok tested now working as should – Yehuda Schwartz Jun 22 '16 at 13:41
It's still just returning a string. It's not doing anything more than returning `x` – 4castle Jun 22 '16 at 13:43
yeh sorry am just a NOOB learning through ansewering – Yehuda Schwartz Jun 22 '16 at 14:15
now does exactly what he asked – Yehuda Schwartz Jun 22 '16 at 14:18
Look at [the answer in the duplicate question](http://stackoverflow.com/a/11433067/5743988). You will find a much nicer algorithm. (Btw, using `eval` is a bad habit. There are only a few specific times when it is appropriate to use it) – 4castle Jun 22 '16 at 14:37

Defining a nested object property in Javascript

2 Answers2