Are there constants in JavaScript?

Question

Is there a way to use constants in JavaScript?

If not, what\'s the common practice for specifying variables that are used as constants?

Answer 1

Another alternative is something like:

var constants = {
      MY_CONSTANT : "myconstant",
      SOMETHING_ELSE : 123
    }
  , constantMap = new function ConstantMap() {};

for(var c in constants) {
  !function(cKey) {
    Object.defineProperty(constantMap, cKey, {
      enumerable : true,
      get : function(name) { return constants[cKey]; }
    })
  }(c);
}

Then simply: var foo = constantMap.MY_CONSTANT

If you were to constantMap.MY_CONSTANT = "bar" it would have no effect as we're trying to use an assignment operator with a getter, hence constantMap.MY_CONSTANT === "myconstant" would remain true.