Using a variable as key in two levels

Question

I want to make a general function where I can print a chosen property from an array with objects.

http://jsbin.com/iNOMaYo/1/edit?js,console,output

Example:

var contacts = [
    {
      name: 'John',
      address:{
        country:'Germany',
        city:'Berlin'
      }
    },
    {
      name: 'Joe',
      address:{
        country:'Spain',
        city:'Madrid'
      }
    }
]

And this is my function:

function print(array, key, index){
  console.log(array[index][key]);
}

So if I want the name for example:

print(contacts, 'name', 0)

I get 'John'.

But how do I do if i want the city instead?

This gets undefined:

print(contacts, 'address.city', 0)

http://jsbin.com/iNOMaYo/1/edit?js,console,output

Any ideas?

Don't think you can do it that way. Have a look at [this answer](http://stackoverflow.com/questions/6491463/accessing-nested-javascript-objects-with-string-key) — putvande, Jan 14 '14 at 14:41
@putvande there was another dup just yesterday that was answered with a brilliant short use of the `.reduce()` Array function. — Pointy, Jan 14 '14 at 14:43
@Pointy That was by me :p http://stackoverflow.com/a/21096145/1903116 — thefourtheye, Jan 14 '14 at 14:44

score 2 · Accepted Answer · answered Jan 14 '14 at 14:42

2

function print(array, key, index){
  var parts = key.split(".");
  var returnValue = array[index];
  for(var i=0;i<parts.length;i++) {
    returnValue = returnValue[parts[i]];
  }
  console.log(returnValue);
}

answered Jan 14 '14 at 14:42

Dominik Goltermann

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of course you would have to catch errors if the key does not exist – Dominik Goltermann Jan 14 '14 at 14:42

score 0 · Answer 2 · answered Jan 14 '14 at 14:52

0

Best thing I could come up at the moment:

http://jsbin.com/iziFevIg/1/edit?html,js,output

Maybe someone else has a better idea.

answered Jan 14 '14 at 14:52

score 0 · Answer 3 · answered Jan 14 '14 at 15:04

My solution is pretty naive, I haven't thought about it in the edge cases but I'm a fan of functional programing so this immediately (leaving immutability aside)

function print(array, key, index) {
  var splitted_key, new_key;

  if (key.indexOf(".") !== -1) { 
    splitted_key = key.split(".");
    new_index = splitted_key.shift();
    new_key = splitted_key.join(".");
    print(array[index], new_key, new_index);
  }
  else {
    console.log(array[index][key]);
  }
}

http://jsbin.com/IFeciJIz/2/edit

Using a variable as key in two levels

3 Answers3