Argument object with default properties and values in ES2015

main.js

function f({a = "I'm A", b = "I'm B"} = {}) {
  console.log(a); // >"I'm C"
  console.log(b); // >"I'm B"
}

f({ a: "I'm C" });

Thanks to destructuring and default parameters, it's possible to have a function accept an object with default properties and values.

I like how compact the syntax is. To achieve similar functionality with ES5 I've previously done something like this:

function f(settings) {
  var a = (typeof settings.a !== 'undefined') ? settings.a : "I'm A";
  var b = (typeof settings.b !== 'undefined') ? settings.b : "I'm B";

  console.log(a); // >"I'm C"
  console.log(b); // >"I'm B"
}

f({ a: "I'm C" });

It's also possible to extend the settings object with a defaults object with the help of a library function. But as you can probably tell, both of those solutions will become rather messy when you have a few more default key/values in your settings object.