Question

How to use enum in JavaScript

Answer 1

// No built-in enum support

const Direction = {
    UP: 'Up',
    DOWN: 'Down',
    LEFT: 'Left',
    RIGHT: 'Right'
};

console.log(Direction.DOWN === 'Down'); 
console.log(Direction.DOWN); 

console.log(Direction.hasOwnProperty('RIGHT')); 
console.log(Direction.hasOwnProperty('Right')); 

console.log(Object.keys(Direction)); 


  
/*
run:
  
true
Down
true
false
[ 'UP', 'DOWN', 'LEFT', 'RIGHT' ]
 
*/

 

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Answer 2

// No built-in enum support

const Days = Object.freeze({
    SUNDAY: 0,
    MONDAY: 1,
    TUESDAY: 2,
    WEDNESDAY: 3,
    THURSDAY: 4,
    FRIDAY: 5,
    SATURDAY: 6
});


console.log(Days.MONDAY);

Days.TUESDAY = 88; 
console.log(Days.TUESDAY);

console.log(Days.FRIDAY === 5); 

console.log(Days.hasOwnProperty('SATURDAY')); 
console.log(Days.hasOwnProperty('ABC')); 
 
console.log(Object.keys(Days)); 

Object.keys(Days).forEach(day => {
    console.log(day);
});


  
/*
run:
  
1
2
true
true
false
[
  'SUNDAY',
  'MONDAY',
  'TUESDAY',
  'WEDNESDAY',
  'THURSDAY',
  'FRIDAY',
  'SATURDAY'
]
SUNDAY
MONDAY
TUESDAY
WEDNESDAY
THURSDAY
FRIDAY
SATURDAY
 
*/

 

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