How to add an ID for each object inside JSON array in JavaScript?

Question

There are many objects in the JSON file that look like I have shown below. I want to give an index number starting from 0 for each of these objects. How can I do it?

[
  {
    "language": "Python",
    "created": "2018-8-27 14:50:31",
    "evaluated": true,
    "hiddenCode": false
  },
  ...
]

What is the reason for adding the IDs to unique Json keys? I don't see the use of an ID as you can access the value with the object key itself. — Sarath Damaraju
– Sarath Damaraju, Commented Aug 27, 2018 at 12:04
exactly what I want to do is to give each object a place called "index" and start the value of this "index" from 0 — jennifercryt
– jennifercryt, Commented Aug 27, 2018 at 12:06
iterating the object with object.keys would be helpful for you. Object.keys(objectName).forEach((each, index) => {/* Your code */}) — Sarath Damaraju
– Sarath Damaraju, Commented Aug 27, 2018 at 12:12

Iurii Tkachenko · Accepted Answer · 2018-08-30 13:27:47Z

2

You can use Array.prototype.map() (MDN) to get new, indexed, array.

var array = [{
  "language": "Python1",
  "created": "2018-8-27 14:50:31",
  "evaluated": true,
  "hiddenCode": false
}, {
  "language": "Python2",
  "created": "2018-8-27 14:50:31",
  "evaluated": true,
  "hiddenCode": false
}]

const indexed = array.map((item, index) => Object.assign(item, { index }))

console.log(indexed)

answered Aug 30, 2018 at 13:27

Iurii Tkachenko

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Comments

Manasi · Accepted Answer · 2018-08-27 11:58:01Z

1

You can loop on the objects and add new property,

var array =[   {
        "language": "Python1",
        "created": "2018-8-27 14:50:31",
        "evaluated": true,
        "hiddenCode": false
    },  {
        "language": "Python2",
        "created": "2018-8-27 14:50:31",
        "evaluated": true,
        "hiddenCode": false
    }
];
for (i = 0; i < array.length; i++) { 
 array[i]["index "] =i;
}
console.log(array);

answered Aug 27, 2018 at 11:58

Manasi

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2 Comments

jennifercryt Over a year ago

I have set this to my own file, but it prints the total number of index numbers, ie each index is output as 39 => "index":39 for each

Manasi Over a year ago

@jennifercryt: can you add your code so that i can check what is wrong

Rupesh Agrawal · Accepted Answer · 2018-08-27 13:10:45Z

0

Probably something like this if you use ES,

You should use map to iterate over your objects and add the property in it

var yourObjects =[   {
        "language": "Python1",
        "created": "2018-8-27 14:50:31",
        "evaluated": true,
        "hiddenCode": false
    },  {
        "language": "Python2",
        "created": "2018-8-27 14:50:31",
        "evaluated": true,
        "hiddenCode": false
    }
];

var i = 0;    
 yourObjects.map(
     (obj) => {
          obj['index'] = i;
          i++
          return obj;
     });
console.log(yourObjects);

edited Aug 27, 2018 at 13:10

Rupesh Agrawal

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answered Aug 27, 2018 at 11:56

Dinosan0908

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1 Comment

Iurii Tkachenko Over a year ago

.map callback function also receives index as a second argument, so no need for extra var i

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