How can I add a field to each row of an array with Javascript?

Question

I have a javascript variable:

var x = 
{"ab":"x",
 "cd":"y",
 "de":"z",
 "answers":[
    {"answerId":222,"answerUId":1,"text":"x"},
    {"answerId":223,"answerUId":2,"text":"A"},
    {"answerId":224,"answerUId":3,"text":"A"}
 ]
}

How can I add a field to each element of the answers array called response with a value of null ?

thefourtheye · Accepted Answer · 2014-07-20 15:14:02Z

8

You can add the new property to the objects, like this

x["answers"].forEach(function(currentObject) {
    currentObject["response"] = null;
});

This iterates through each and every object and adds the response property to each of them.

answered Jul 20, 2014 at 15:14

thefourtheye

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3 Comments

hutingung Over a year ago

forEach is native javascript

p.s.w.g Over a year ago

@Otanaught It just requires a browser that supports ECMAScript 5.1: Array.prototype.forEach

Ota Over a year ago

Oh i see, just checked the MDN about forEach. Watch out for browser backwards compatibility.

Ota · Accepted Answer · 2014-07-20 15:16:33Z

3

Plain javascript:

for (key in x['answers']) {
    x['answers'][key]['response'] = null;
}

answered Jul 20, 2014 at 15:16

Ota

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4 Comments

thefourtheye Over a year ago

Iterating an array with for..in is bad.

Ota Over a year ago

@thefourtheye could you please explain why?

thefourtheye Over a year ago

Just check the boxed items in this section

Ted Hopp Over a year ago

@thefourtheye - The caution in the boxed items recommends against using for..in only "where index order is important". I don't see that index order is important here.

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