Javascript Constants

constants.js

// Ever need to create constants in javascript? 

// Option 1:

  // Browser Support: ie9+ ff4+ chrome6+ opera12+ safari 5.1+

  // You must wrap your constants variables in an object:

var constants = 
  {
    CONSTANT1: 'constant value',
    CONSTANT2: 2
  };
  
  // Freeze the object. This makes it immutable, giving it the appearance of constants.

Object.freeze(constants);

  // Now, changing a variable will silently fail.

constants.CONSTANT1 = true;
console.log(constants.CONSTANT1); // prints 'constant value'

constants.CONSTANT2 = '2';
console.log(typeof constants.CONSTANT2); // prints 'number'

// option 2:

  // Object.defineProperty

  // Browser Support: ie9+(8 with issues) ff4+ chrome5+ opera11.6+ safari 5.1+
  
Object.defineProperty(this, 'varName', {
  enumerable: true,
  configurable: true
  writable: false,
  value: 2 // The value the constant should be set to.
});

console.log(varName); // prints 2

varName = 3

console.log(varName); // prints 2