Javascript object literal - possible to add duplicate keys?

Question

In javascript, is is possible to add duplicate keys in object literal? If it is, then how could one achieve it after the object has been first created.

For example:

exampleObject['key1'] = something;
exampleObject['key1'] = something else;

How can I add the second key1 without overwriting the first key1?

@Ville: How would you want to access the value and know which version it is? — lxg
– lxg, Commented Aug 5, 2016 at 13:12
I'm about to generate an xml from that object. And that xml contains elements that have exactly the same name (Though they contain atttributes with different values). Mm.. maybe I need to generate the xml first without those duplicates, and then try to add those duplicate elements later in the process. — Ville Miekk-oja
– Ville Miekk-oja, Commented Aug 8, 2016 at 7:16
Does this answer your question? JS associative object with duplicate names — Ganesh Chowdhary Sadanala
– Ganesh Chowdhary Sadanala, Commented Sep 19, 2020 at 5:57

Nicholas Robinson · Accepted Answer · 2016-08-05 13:13:59Z

15

No it is not possible. It is the same as:

exampleObject.key1 = something;
exampleObject.key1 = something else; // over writes the old value

I think the best thing here would be to use an array:

var obj = {
  key1: []
};

obj.key1.push("something"); // useing the key directly
obj['key1'].push("something else"); // using the key reference

console.log(obj);

// ======= OR ===========

var objArr = [];

objArr.push({
  key1: 'something'
});
objArr.push({
  key1: 'something else'
});

console.log(objArr);

answered Aug 5, 2016 at 13:13

Nicholas Robinson

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Comments

hsz · Accepted Answer · 2016-08-05 13:12:43Z

6

You cannot duplicate keys. You can get the value under the key1 key and append the value manually:

exampleObject['key1'] = something;
exampleObject['key1'] = exampleObject['key1'] + something else;

Another approach is the usage of an array:

exampleObject['key1'] = [];
exampleObject['key1'].push(something);         
exampleObject['key1'].push(something else);

answered Aug 5, 2016 at 13:12

hsz

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1 Comment

David H. Over a year ago

I think it's because you cannot just do arithmetic operations with any variable. The user did not specify what type of variable "something" is. However, the array implementation would work.

Dorian Turba · Accepted Answer · 2020-02-20 10:39:38Z

3

In javascript having keys with same name will override the previous one and it will take the latest keys valuepair defined by the user.

Eg:

var fruits = { "Mango": "1", "Apple":"2", "Mango" : "3" }

above code will evaluate to

var fruits = { "Mango" : "3" , "Apple":"2", }

edited Feb 20, 2020 at 10:39

Dorian Turba

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answered Feb 20, 2020 at 9:40

shweta ghanate

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