Javascript add properties with the same name to an object - Stack Overflow

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    var elements = document.getElementsByClassName("someClass");
    var obj = {};
    for (var i = 0; i < elements.length; i++){
        obj.userId = elements[i].id 
    } 

// output: obj = {userId: 1, userId: 2, userId: 3.....etc}

Is it possible in some way? Thanks.

    var elements = document.getElementsByClassName("someClass");
    var obj = {};
    for (var i = 0; i < elements.length; i++){
        obj.userId = elements[i].id 
    } 

// output: obj = {userId: 1, userId: 2, userId: 3.....etc}

Is it possible in some way? Thanks.

• javascript
• object
• properties

Share Improve this question Follow asked Dec 9, 2015 at 10:06 Serhio g. LazinSerhio g. Lazin 9,65266 gold badges2727 silver badges3333 bronze badges 4

• I think you can not use same key, it will override. obj["userId"] = elements[i].id ; – Shubham Commented Dec 9, 2015 at 10:07
• it is not possible in an object. please use an array for this purpose like ` [{userId: 1}, {userId: 2}, {userId: 3}]`. – Nina Scholz Commented Dec 9, 2015 at 10:08
• key name of same object must be unique – Anik Islam Abhi Commented Dec 9, 2015 at 10:08
• So answer is "not possiple". You could say obj ['userId'+i]=elements [i].id – el3ien Commented Dec 9, 2015 at 10:21

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2 Answers 2

Sorted by: Reset to default 4

keys in Object must be unique, you can try use Array, like this

var obj = [];
var data = {};
for (var i = 0; i < elements.length; i++) {
   data = {
     userId: elements[i].id 
   };
   obj.push(data);
} 

// [ {userId: 1}, {userId: 2} ... ] 

The JSON RFC says "the names within an object SHOULD be unique" - see here for more info however should your object have a duplicate key the last occurrence will be used.

An array would be a better solution for your data.

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