JS: Enum: Creating enum functionality in JS | JavaScript
Enum in JavaScript
JavaScript has no default support of enum unlike other progrmming languages like c++, c# etc. Enum functionality can be achieved using Object.freeze static function in JavaScript.
var Fruits = Object.freeze({"Mango":1, "Orange":2, "Apple":3, "Pineapple" :4, "Grape": 5, "Banana": 6});
var f1 = Fruits.Orange;
var f2 = 5;// Grape
if(f1 === Fruits.Orange)
console.log('Chose Orange');
if(f2 === Fruits.Grape) //f2 === 5 and Fruits.Grape === 5
console.log('also Grape');
Chose Orange
also Grape
Iterating Enum in loops
var Fruits = Object.freeze({"Mango":1, "Orange":2, "Apple":3, "Pineapple" :4, "Grape": 5, "Banana": 6});
for(var f in Fruits)
console.log(Fruits[f], f)
1 Mango
2 Orange
3 Apple
4 Pineapple
5 Grape
6 Banana
Fruits is itereted just like any other Object.
The difference is that Fruits properties have been made readonly using Object.freeze function.
Using Enum as Flags
Using enum to allow multiple values in a single variable but the upcoming value must double the previous value
var Fruits = Object.freeze({"Mango":1, "Orange":2, "Apple":4, "Pineapple" :8, "Grape": 16, "Banana": 32, "Cherry": 64});
var yellowFruits = Fruits.Mango | Fruits.Banana;
if(yellowFruits & Fruits.Mango)
console.log('Mango is a yellow fruit');
Mango is a yellow fruit
Mango and Banana are assigned to yellowFruits using | operator.
Similarly, we may also assign
var Fruits = Object.freeze({"Mango":1, "Orange":2, "Apple":4, "Pineapple" :8, "Grape": 16, "Banana": 32, "Cherry": 64});
var yellowFruits = Fruits.Mango | Fruits.Banana;
var redFruits = Fruits.Apple | Fruits.Cherry;
if(yellowFruits & Fruits.Mango)
console.log('Mango is a yellow fruit');
else
console.log('Mango is not a yellow fruit');
if(redFruits & Fruits.Mango)
console.log('Mango is a red fruit');
else
console.log('Mango is not a red fruit');
Mango is a yellow fruit
Mango is not a red fruit