Avoiding Pitfalls with Assigning Falsy Values in Defaults?

Question

Is there anyway that we can deal with falsy values in || operators that are lazily evaluated?

So, for example if we have:

function isOldEnough(age) {
   age = age || 18;
   return age;
}

isOldEnough(0) // returns 18 because 0 is falsy

In ES6, you can simply declare it like

function isOldEnough(age = 18) { ... }

Is there anythning we can do in ES5 to avoid this issue?

Answer 1

Something like (if I understood correctly):

function isOldEnough(age) {
  var age = typeof age === "number" ? arguments[0] : 18;
  return age; 
}

isOldEnough(null) // returns 18
isOldEnough("") // returns 18
isOldEnough(undefined) // returns 18
isOldEnough(0) // returns 0

Could be further improved with checking if age is equal to or greater than zero etc