Adding new property to object

Question

I have a javascript object which I use as type of map with key value pairs.

Population of this map occurs when value is injected to it from controller :

var people = {"2":"Brad","3":"Antonio","5":"Stacy","6":"Marry","1":"Jim"}

I want to create a new object but with one more entry i.e in pseudo code

var new_people = people + {11: "John"}

I tried to copy people to new people first and then :

new_people.\"11\" = "John"

and

new_people."11" = "John"

Both produce failure. While any string instead of number works i.e

new_people.anystring = "John"

var new_people = {"2":"Brad","3":"Antonio","5":"Stacy","6":"Marry","1":"Jim", "anystring":"John"}

It's not quite true that any string will work. 1string is a string, but new_people.1string won't work. — Paul D. Waite
– Paul D. Waite, Commented Mar 22, 2013 at 13:26
possible duplicate of how to access any element using javascript, if elemet is having special characters and What is the most efficient way to clone a JavaScript object?. — Felix Kling
– Felix Kling, Commented Mar 22, 2013 at 13:32
In your example new_people.anystring = "John", anystring is a sequence of characters, but it is not a string in the sense of a JavaScript data type. It is an identifier name. — Felix Kling
– Felix Kling, Commented Mar 22, 2013 at 13:35

akaIDIOT · Accepted Answer · 2013-03-22 13:24:54Z

6

You could use indexing:

new_people['11'] = 'John';

answered Mar 22, 2013 at 13:24

akaIDIOT

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gdoron · Accepted Answer · 2013-03-22 13:25:27Z

2

You just need to add a key value to the object:

people['11'] = "John";

If the key was a valid identifier name(not a number) you could have used this:

people.key = "John";

You have to use the indexes when it's not a valid variable name:

people["~!#$#$#HV"] ="some value";

answered Mar 22, 2013 at 13:25

gdoron

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Comments

JamesOR · Accepted Answer · 2013-03-22 16:00:09Z

2

You will have a problem because variables hold references when storing objects. By mutating new_people, you are also mutating people.

var people = {"1":"James"}
console.log(people);       // Object {1: "James"}
var new_people = people;
new_people["2"] = "Jimmy";
console.log(people);       // Object {1: "James", 2: "Jimmy"}
console.log(new_people);   // Object {1: "James", 2: "Jimmy"}

You'll need to clone the object first then mutate the clone so you don't affect the original object.

One easy way to do that is using the underscore.js extend() method like this:

var new_people = _.extend({}, people, {"2": "Jimmy"});
console.log(people);       // Object {1: "James"}
console.log(new_people);   // Object {1: "James", 2: "Jimmy"}

Or similarly, with jQuery extend() like this:

var new_people = $.extend({}, people, {"2": "Jimmy"});
console.log(people);       // Object {1: "James"}
console.log(new_people);   // Object {1: "James", 2: "Jimmy"}

edited Mar 22, 2013 at 16:00

answered Mar 22, 2013 at 13:32

JamesOR

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3 Comments

Paul D. Waite Over a year ago

Yup: the line var new_people = people + {11: "John"} in the question doesn't create a new object. (It actually creates a string.)

Jeff Shaver Over a year ago

@PaulD.Waite the OP indicated that var new_people = people + {11: "John"} was pseudo code.

Paul D. Waite Over a year ago

@JeffShaver: ah, yes I see. Hadn't noticed that.

Khanh Tran · Accepted Answer · 2013-03-22 13:59:01Z

0

@Gandalf StormCrow Here is a code: jsfiddle

var people = {"2":"Brad","3":"Antonio","5":"Stacy","6":"Marry","1":"Jim"};

var newpeople = {"11": "John"};
jQuery.extend(people, newpeople);
//Now: people = {"2":"Brad","3":"Antonio","5":"Stacy","6":"Marry","1":"Jim","11": "John"}

for(var i in people){
  alert(people[i]);  
};

answered Mar 22, 2013 at 13:59

Khanh Tran

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