Check if a variable is defined in CoffeeScript

Jun 4, 2013

In JavaScript it’s pretty common to check if a variable has been created. You would usually perform the check with the following code:

if (type someVariable !== "undefined") {
  // code goes here

}

This is the equivalent syntax in CoffeeScript.

if someVariable?
  # code goes here

This will generate the following JavaScript:

if (typeof someVariable !== "undefined" && someVariable !== null) {
  // code goes here

}

Much neater. Happy coding.