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1

I have a nested Javascript object like

var data = { 'name':    { 'heading': 'Name', 'required': 1, 'type': 'String' },
             'profile': {
                  'age':   { 'heading': 'Age', 'required': 0, 'type': 'Number' },
                  'phone': { 'heading': 'Phone', 'required': 0, 'type': 'String'},
                  'city':  { 'heading': 'City', 'required': 0, 'type': 'String'},
                  },
             'status':  { 'heading': 'Status', 'required': 1, 'type': 'String' }
           };

Here, I can access the fields as data.profile.age.type or data.name.type. No Issues And if I have dynamic variable names, I can access as below. Again, No Problems.

f = 'profile'; data[f].age.type

But, here I have variable names like 'name', 'profile.age', 'profile.city' etc and obviously I cannot access them as f = 'profile.age'; data[f].type which will not work.

Can anyone guide me how to access them (get/set) in the most straight-forward and simple way?

Note: I tried this and it works for get.

data.get = function(p) { o = this; return eval('o.'+p); };
f = 'profile.age'; data.get(f).name;

though set does not seem to be simple enough. Please let me know, if there are better solutions for get and set as well.

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1  
You were right to ask this question on SO. Anytime you find yourself using eval in Javascript, you are almost certainly doing the wrong thing. –  Bobby Eickhoff Dec 13 '10 at 17:40
 
Thanks for letting me know about eval. May be eval is evil! :-) –  rsmoorthy Dec 13 '10 at 17:53
 
You said it. Take a look at the last suggestion offered here: javascript.crockford.com/code.html –  Bobby Eickhoff Dec 13 '10 at 18:26

3 Answers

up vote 4 down vote accepted

Don't use eval unless absolutely necessary. :) At least in this case, there are better ways to do it -- you can split the nested name into individual parts and iterate over them:

data.get = function(p) {
  var obj = this;

  p = p.split('.');
  for (var i = 0, len = p.length; i < len - 1; i++)
    obj = obj[p[i]];

  return obj[p[len - 1]];
};

data.set = function(p, value) {
  var obj = this;

  p = p.split('.');
  for (var i = 0, len = p.length; i < len - 1; i++)
    obj = obj[p[i]];

  obj[p[len - 1]] = value;
};
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Thanks. Very fast response and helpful. –  rsmoorthy Dec 13 '10 at 17:51
up vote 5 down vote

You can just nest the brackets:

var a = 'name', b = 'heading';
data[a][b]; // = `Name`
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1  
this is not answering the question at all... –  vsync Sep 21 '11 at 11:53
1  
@vsync: Sure it does. I'm saying that rather than var a='name.heading'; data[a], you can use successive sets of brackets to access deeper levels of the object. So if you know you're looking for something in the profile object, var a='profile',b='age'; data[a][b] works. Obviously, if you need to handle an arbitrary string, the other answers show how to do that. This is an alternative if someone doesn't need the complexity of parsing arbitrary "a.b.c.d" strings. –  josh3736 Sep 21 '11 at 14:43
up vote 2 down vote

Perhaps a function that takes in the path to the property you're interested in and breaks it up into tokens representing properties. Something like this (this is very rough, of course):

data.get = function(path) {
  var tokens = path.split('.'), val = this[tokens[0]];
  if (tokens.length < 2) return val;
  for(var i = 1; i < tokens.length; i++) {
     val = val[tokens[i]];
  }
  return val;
}

example:

   var f = 'one.two';
   var data = { one: {two:'hello'}};
   data.get = /* same as above */;

   var val = data.get(f);
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