How to increment a value inside an object variable

Question

I have the following.

var dataset = {val1 : 0, val2 : 0, val3 : 0};
var person = [];
var totalPeople = 10;

for(var i = 0; i <totalPeople; i++) {
   person[i] = dataset; 
}

Why i chose this approach, click here .

I'm trying to make one of the values auto increment inside another for loop.

I've tried the following approaches to no avail.

person[1]{val1 : 0,
          val2 : 0,
          val3 : val3 + 1};

person[1]{val1 : 0,
          val2 : 0,
          val3 : person[1].val3 + 1};

person[1].val3 = person[1].val3 + 1;

any ideas?

Are you trying to increment the field name, or the field value? — Josiah Ruddell, Sep 16 '14 at 19:40
Juvian, I'll expand the code a little. U_mulder, I was writing with the intention of Jquery.. but this was an answer given to another question. oops if it is pure js [newby :) ] — Swift, Sep 16 '14 at 19:43

score 7 · Answer 1 · answered Sep 16 '14 at 19:40

7

This should be the right:

person[1].val3 += 1;

answered Sep 16 '14 at 19:40

reyaner

2,799
1
12
17

score 2 · Answer 2 · answered Sep 16 '14 at 19:39

2

This should work.

var dataset = {val1 : 0, val2 : 0, val3 : 0};
var person = [];
var totalPeople = 10;

for(var i = 0; i <totalPeople; i++) {
   dataset[i].val3 ++; 
}

Could you explain more what you are trying to achieve?

answered Sep 16 '14 at 19:39

Santiago Nicolas Roca

399
3
9

1

Is there a more elegant way to do this? perhaps some ES6 magic? – zero_cool Nov 06 '17 at 20:11

score 1 · Accepted Answer · edited May 23 '17 at 12:10

Totally sorry. The solution that you're referring to here was posted by me and is incorrect. I just updated my answer in that post.

Don't use the array initialization style that I originally posted:

var dataset = {val1 : 0, val2 : 0, val3 : 0};
var person = [];
var totalPeople = 10;

for(var i = 0; i < totalPeople; i++) {
  person[i] = dataset; // this assigns the *same* object reference to every 
                       // member of the person array.

}

This is the correct way to initialize your person array:

var person = [];
var totalPeople = 10;

for(var i = 0; i < totalPeople; i++) {
  person[i] = {val1 : 0, val2 : 0, val3 : 0}; // do this to create a *unique* object 
                                              // for every person array element
}

If you use the correct array initializtion shown directly above, then you can increment val3 like this with each loop iteration:

var person = [];
var totalPeople = 10;

for(var i = 0; i < totalPeople; i++) {
  person[i] = {val1 : 0, val2 : 0, val3 : 0};
  person[i]['val3'] = i;
}

Sorry again for the bad information that I provided in the other post. (All other info is correct. Just the array initialization code was bad.) I hope this updated information helps.

How to increment a value inside an object variable

3 Answers3