Variable name getting added instead of its value, javascript

Question

I have a problem while adding values to a JavaScript object: the value to add is a key,value pair. Here is sample:

//JavaScript object

var cart=new Object();

function add()
{
  var rating="1"
  var category="somecat";
  var user="user1";

   if(cart[user]==null)

        cart[user]={category:rating};

   else

         cart[user][category]=rating;
 }

What I was expecting is that if user exists in cart object then value for his particular should get replaced, and if user doesn't exist then new user and category should be added.

The code is working fine when user already exists. Problem is, when I am adding a new element with cart[user]={category:rating} then its adding the variable name as key i.e. category , not the value inside it ("somecat").

Is there any way to do this using json, jquery or javascript itself?

Is there any way to assign value inside the variable?

Quentin · Accepted Answer · 2012-09-12 10:44:44Z

7

There is no way to use a variable to define a property name inside object literal notation. It accepts identifiers or strings, but both identify property names, not variables.

You have to create the object then add the property:

if(!cart[user]) { 
   cart[user] = {};
}
cart[user][category] = rating;

answered Sep 12, 2012 at 10:44

Quentin

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3 Comments

Nikhil Rupanawar Over a year ago

Thanks ! :) means it treats everything as property name. (literal). that's nice to know . thanks

Nikhil Rupanawar Over a year ago

I have another query . cart[user]={category:rating}; in this case the value of rating is getting added i.e: "1" . how this?

Quentin Over a year ago

Because that is a value, not a property name.

James Montagne · Accepted Answer · 2012-09-12 13:55:08Z

3

You will need to replace

{category:rating}

with

var obj = {};
obj[category] = rating;

answered Sep 12, 2012 at 13:55

James Montagne

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Comments

slashnick · Accepted Answer · 2012-09-12 14:01:49Z

0

When creating an object literal the key must be a string, so in your code it will be "category". If instead you do:

  var rating="1"
  var category="somecat";
  var user="user1";

   if( !cart[user] ) {     
        cart[user]={};  
   }

   cart[user][category]=rating;

That will initialise a non existing user to an empty object and then add the category.

answered Sep 12, 2012 at 14:01

slashnick

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