How to refer to the object property if the property name can be any

Question

I have, for example, the following array of objects:

data = [{id:name1, num1:12, num2:8},
        {id:name2, num1:5, num2:13},
        {id:name3, num1:21, num2:4}];

I am wondering, how can I refer only to property "num1" of all objects or "num2", considering, that I don't know the exact name of the property. So if I want to find the Sum of all num2 I cannot do it simply writing the following piece of code:

data.forEach(function(obj) {
Sum += obj.num2;
};

Cause "num2" may not be called "num2" but any other name, depending on the generated report (data is taken from the Microstrategy reporting system). And it is inconvenient to change the code every time just to meet the property name.

Any help is highly appreciated! :)

Why don't you put all the numbers in an array inside the object instead of the current structure? Example: `data = [{id: 'x', num: [12, 8]}];` — Derek Pollard, Mar 24 '16 at 16:04
Will the custom name for the "num2" key always be placed as the 3rd key in every object? — Jonathan Nielsen, Mar 24 '16 at 16:06
Use `object[variable_with_prop_name]`. BTW `object.property` is just a shortcut to `object["property"]`. — Oleg V. Volkov, Mar 24 '16 at 16:09
@OliverQueen, because I get the data from the report in csv format first, and in that case it will have every value in the row in separate column, with own property name :/ — Slava32, Mar 24 '16 at 16:23
@JonathanNielsen, yes, it will be always placed as the 3rd key in every object. — Slava32, Mar 24 '16 at 16:25
@user7, I want to be able to sum up the 2nd and 3rd columns with numeric values. To get Sum_num1 and Sum_num2, for example. — Slava32, Mar 24 '16 at 16:28
I guess unless you have the values in an array, you cannot do it as in javascript, properties order in an object cannot be guaranteed. — user7, Mar 24 '16 at 16:33
See: [Elements order in a “for (… in …)” loop](http://stackoverflow.com/questions/280713/elements-order-in-a-for-in-loop) "Currently all major browsers loop over the properties of an object in the order in which they were defined." — Roberto, Mar 24 '16 at 16:34
@user7, well, I did it, so it's possible :) Everything works now. — Slava32, Mar 29 '16 at 11:52

Dan · Answer 1 · 2016-03-24T16:21:31.430

This may be overkill, but this is what I would do to create a Sum object from the original

data = [{
  id: 'name1',
  num1: 12,
  num2: 8
}, {
  id: 'name2',
  num1: 5,
  num2: 13
}, {
  id: 'name3',
  num1: 21,
  num2: 4
}];

var Sum = {};
data.forEach(function(obj) {

  var keys = Object.keys(obj);
  keys.forEach(function(k) {
  if( i )
    if (Sum.hasOwnProperty(k)) {
      Sum[k] += obj[k];
    } else {
      Sum[k] = obj[k];
    }
  })
})

console.log(Sum);

https://jsfiddle.net/d6vttp9v/

Note: this also sums the string field, so its kind of nonsense, but you could easily specify an array of column to exclude (exercise for the reader).

So this answer doesn't get you exactly what you want (I'm not sure exactly what you want), but hopefully its a good step in right direction.

score -2 · Answer 2 · edited Jun 20 '20 at 09:12

-2

You can access an objects properties like so:

var x = { someProp1: 'x', someProp2: 'y' };
for(prop in x) {
  console.log(prop);
}

Heres a handy reference

If this question is more generally about schema changes in JSON objects and whats the best approach to that, heres an angle I use.

for example the ajax call getPeople

myApp.ajaxSchemas.getPeople = {
  NAME: 'Name',
  AGE: 'Age'
};

I would then refer to the schema in my code:

someObject[myApp.ajaxSchemas.getPeople.NAME];

This means that when theres a schema change it is managed in one place, the myApp.ajaxSchemas.getPeople definition.

I hope this helps.

Rhys

edited Jun 20 '20 at 09:12

Community

1
1

answered Mar 24 '16 at 16:07

Rhys Bradbury

1,566
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Why have I been downvoted? – Rhys Bradbury Mar 24 '16 at 16:14
have no idea. I cannot vote yet, because have not enough reputation. Thx for answer, I'll try it :) – Slava32 Mar 24 '16 at 16:17
Because you didn't understand question. – Oleg V. Volkov Mar 24 '16 at 16:18
I see. I will update my answer – Rhys Bradbury Mar 24 '16 at 16:25
I also think you were downvoted because `for..in` would be a better loop choice for something like this – Derek Pollard Mar 24 '16 at 16:26
Oliver I am trying to express that the result of Object.keys is an array – Rhys Bradbury Mar 24 '16 at 16:28
My answer has been updated – Rhys Bradbury Mar 24 '16 at 16:29
`Object.prototype.keys` does not exist, have you tested your code before posting it? `Object.keys(x)` is what you're looking for – floribon Apr 14 '16 at 21:45
Ops, i ment the static `func` `Object.keys()` – Rhys Bradbury Apr 15 '16 at 10:14
.....? answer updated... – Rhys Bradbury Apr 18 '16 at 14:28

How to refer to the object property if the property name can be any

2 Answers2