How do I create JavaScript array (JSON format) dynamically?

Question

I am trying the create the following:

var employees = {
  "accounting": [ // accounting is an array in employees.
    {
      "firstName": "John", // First element
      "lastName": "Doe",
      "age": 23
    },

    {
      "firstName": "Mary", // Second Element
      "lastName": "Smith",
      "age": 32
    }
  ] // End "accounting" array.                                  

} // End Employees

I started with

 var employees = new Array();

How do I continue to create the array dynamically (might change firstName with variable)? I don't seem to get the nested array right.

The preferred way of creating a array in javascript is var employess = []; not var employees=new Array(); — Mattias Jakobsson, Feb 12 '10 at 10:08

Alex · Accepted Answer · 2018-01-04T15:38:12.533

Our array of objects

var someData = [
   {firstName: "Max", lastName: "Mustermann", age: 40},
   {firstName: "Hagbard", lastName: "Celine", age: 44},
   {firstName: "Karl", lastName: "Koch", age: 42},
];

with for...in

var employees = {
    accounting: []
};

for(var i in someData) {    

    var item = someData[i];   

    employees.accounting.push({ 
        "firstName" : item.firstName,
        "lastName"  : item.lastName,
        "age"       : item.age 
    });
}

or with Array.prototype.map(), which is much cleaner:

var employees = {
    accounting: []
};

someData.map(function(item) {        
   employees.accounting.push({ 
        "firstName" : item.firstName,
        "lastName"  : item.lastName,
        "age"       : item.age 
    });
}

score 48 · Answer 2 · answered Mar 21 '14 at 21:07

48

var accounting = [];
var employees = {};

for(var i in someData) {

    var item = someData[i];

   accounting.push({ 
        "firstName" : item.firstName,
        "lastName"  : item.lastName,
        "age"       : item.age 
    });
}

employees.accounting = accounting;

answered Mar 21 '14 at 21:07

Chase

481
4
2

this is better than the above example, this also tells how to add the array dynamically. – Harry Jul 30 '14 at 04:49
but if i am passing it in another file, it is undefined. – Abhishek Tripathi Feb 16 '15 at 15:34
What if I need that array's name to be dynamic? – easythrees Apr 05 '17 at 01:22

score 15 · Answer 3 · edited Jun 24 '17 at 18:24

15

var student = [];
var obj = {
    'first_name': name,
    'last_name': name,
    'age': age,
}
student.push(obj);

edited Jun 24 '17 at 18:24

Floern

33,559
24
104
119

answered Jun 24 '17 at 18:19

Venu Upadhyay

161
1
3

alexventuraio · Answer 4 · 2016-06-19T21:28:11.903

8

What I do is something just a little bit different from @Chase answer:

var employees = {};

// ...and then:
employees.accounting = new Array();

for (var i = 0; i < someArray.length; i++) {
    var temp_item = someArray[i];

    // Maybe, here make something like:
    // temp_item.name = 'some value'

    employees.accounting.push({
        "firstName" : temp_item.firstName,
        "lastName"  : temp_item.lastName,
        "age"       : temp_item.age
    });
}

And that work form me!

I hope it could be useful for some body else!

edited Jun 19 '16 at 21:28

answered Feb 24 '16 at 18:56

alexventuraio

8,126
2
30
35

From where the variable item is coming from? – Irfan Raza Jun 18 '16 at 13:21
its now fixed @IrfanRaza – alexventuraio Jun 19 '16 at 21:28

How do I create JavaScript array (JSON format) dynamically?

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