JS: default parameter

With default parameters in ES2015, checks in the function body are no longer necessary as per the example shown below:

function AnyFunction(pickUpThisClass) {
    pickUpThisClass=    typeof (pickUpThisClass) !== 'undefined' ?
                        pickUpThisClass :
                        'default-class';
    console.log(pickUpThisClass);
}

Now, you can assign the default value in the function head:

function multiply(a, b = 1) {
  return a * b
}

multiply(5, 2)          // 10
multiply(5)             // 5
multiply(5, undefined)  // 5

More info on MDN Web Docs:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters