CODEWITHSUNDEEP
javascript
wong2
wong2

Reputation: 35730

JavaScript enumerator?

I want to define a list of constants that have continuous integer value, for example: 

var config.type = {"RED": 0, "BLUE" : 1, "YELLO" : 2};

But it's boring to add a "XX" : y every time I need to add a new element in it.
So I'm wondering is there something like enumerator in C so I can just write:
var config.type = {"RED", "BLUE", "YELLO"} and they are given unique integer value automatically.

Upvotes: 15

Views: 18312

Answers (5)

Darlan Dieterich
Darlan Dieterich

Reputation: 2537

Define the Enum:

var type = {
  RED: 1,
  BLUE: 2, 
  YELLO: 3 
};

get the color:

var myColor = type.BLUE;

Upvotes: 2

Locksfree
Locksfree

Reputation: 2702

You could also try to do something like this:

function Enum(values){
    for( var i = 0; i < values.length; ++i ){
        this[values[i]] = i;
    }
    return this;
}
var config = {};
config.type = new Enum(["RED","GREEN","BLUE"]);
// check it: alert( config.type.RED );

or even using the arguments parameter, you can do away with the array altogether:

function Enum(){
    for( var i = 0; i < arguments.length; ++i ){
        this[arguments[i]] = i;
    }
    return this;
}
var config = {};
config.type = new Enum("RED","GREEN","BLUE");
// check it: alert( config.type.RED );

Upvotes: 17

user113716
user113716

Reputation: 322502

I suppose you could make a function that accepts an Array:

function constants( arr ) {

    for( var i = 0, len = arr.length, obj = {}; i < len; i++ ) {
        obj[ arr[i] ] = i;
    }
    return obj;
}


var config.type = constants( ["RED", "BLUE", "YELLO"] );

console.log( config.type );  // {"RED": 0, "BLUE" : 1, "YELLO" : 2}

Or take the same function, and add it to Array.prototype.

Array.prototype.constants = function() {

    for( var i = 0, len = this.length, obj = {}; i < len; i++ ) {
        obj[ this[i] ] = i;
    }
    return obj;
}


var config.type = ["RED", "BLUE", "YELLO"].constants();

console.log( config.type );  // {"RED": 0, "BLUE" : 1, "YELLO" : 2}

Upvotes: 1

Marc B
Marc B

Reputation: 360702

Use an array ([]) instead of an object ({}), then flip the array to swap keys/values.

Upvotes: 2

Naftali
Naftali

Reputation: 146310

Just use an array:

var config.type =  ["RED", "BLUE", "YELLO"];

config.type[0]; //"RED"

Upvotes: 5

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