CODEWITHSUNDEEP
javascriptprototype-programming
RRaney
RRaney

Reputation: 31

var prototypes with a default value

I saw a solution from Stijn de Witt for definine enums in Javascript.

var SIZE = {
  SMALL : {value: 0, name: "Small", code: "S"},    
  MEDIUM: {value: 1, name: "Medium", code: "M"},    
  LARGE : {value: 2, name: "Large", code: "L"}
};

Usage:

alert(SIZE.SMALL.value);
...

I have been trying to adapt this to allow me to define Users.

var RRR : {name: "RRRaney:, number: 2, date: 2007};

This works as I would expect:

alert(RRR.name + " " + RRR.date); //to display the text "RRRaney 2007".

I would like to try to define the .name as the default, so I could write something like:

alert(RRR + " " + RRR.date);      //to display the text "RRRaney 2007".

or just

alert(RRR);                      // to display the text "RRRaney".

Upvotes: 2

Views: 475

Answers (3)

James Montagne
James Montagne

Reputation: 78650

Well this might be a bad idea and I have no idea how other browsers will handle this, but this works in chrome...

http://jsfiddle.net/yvgj8/

var RRR = {
             name: "RRRaney", 
             number: 2, date: 2007, 
             toString: function(){
                return this.name;
             }
          };

alert(RRR + " " + RRR.date);

Didn't think this would actually work, so chances are it won't in other browsers.

Upvotes: 3

vhallac
vhallac

Reputation: 13907

I am not sure if I should write this, since it is in the same spirit of kingjiv's answer. But it is slightly different, so I decided to put it here in any case.

function enum(name, value, date) {
    this.name = name;
    this.value = value;
    this.date = date;
}
enum.prototype.toString = function() {
    return this.name;
}

Usage is:

RRR = new enum("RRRaney", 2, 2007);
alert(RRR + " " + RRR.date);

Edit: An unfortunate choice of object name. Apparently enum is a reserved keyword in javascript 1.3+, so the code fails in internet explorer. You need to rename it to Enum or some such if you want to use it.

Upvotes: 0

user113716
user113716

Reputation: 322492

The only way I can think of would be hackish and undesirable, but here it goes:

var RRR = new String("RRRaney:");
RRR.date = "2007";

alert( RRR + RRR.date );

Instead of using a string literal for your name, this is borrowing a String wrapper object to be your object with a value of "RRRaney:", and adding a date property to that wrapper object.

It gives the result you want, but seriously, don't do it. Just stick with a typical object literal.

You mentioned prototype in the title of your question.

If you were thinking of a Constructor function that gives a default name for the objects it creates, that's a different story:

var MyConstructor = function( date ) {
    this.date = date;
};

MyConstructor.prototype.name = "RRRaney:";

var inst = new MyConstructor( "2007" );

But it doesn't represent RRR in the manner you want.

Upvotes: 1

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