In javascript, we often want to pass objects as arguments to our functions. Since ES6, we can destructure those object for better readability. Flow is a static type checker for javascript maintained by Facebook. Let’s look at integrating the two.

Object destructuring in ES6 functions looks like so:

function coolKids({name, isCool}) {
  console.log(name, isCool);

coolKids({name: 'Rob', isCool: false});
// Rob, false

This is nice, as we can see when calling the coolKids function the key/value pairs. Much easier to gather what the function’s purpose is.

Now, let’s add some default values, which we can now do inside the function definition object itself!

function coolKids({name = 'The Dude', isCool = true}) {

Finally, we want to setup type checking using Flow. We can do that by mapping our object to a second type object.

function coolKids({name = 'The Dude', isCool = true}: {name: string, isCool: boolean) {

And there you have it! Some further reading on Flow types and destructuring for your learning pleasure.