Ryan Burnette

JavaScript Arrow Function Expressions

JavaScript arrow function expressions were introduced in ECMAScript 2016 (ES6).

I find them hard to read. I am also frustrated at how they have, for some reason, become the default function declaration. I see that they have a role, but I don’t think we should just use them because they look cool.

When I Use Arrows

For me, there are two reasons to use arrows.

  1. When I need the parent lexical context
  2. When I want to save time with a one-liner

I can demonstrate both by converting the psuedo-code block below to use an arrow.

Disclaimer

I don’t use arrows for fun. If I don’t need an arrow, I use conventional function declaration.

Before

function myAwesomeFunction() {
  var _this = this;
  promiseReturner().then(function (foo) {
    _this.bar(foo);
  });
}

After

function myAwesomeFunctionWithArrows() {
  promiseReturner().then((foo) => this.bar(foo));
}

Babel

Another argument against arrows for me is browser support. If I use arrows in my front-end JavaScript, I have to think about which browsers support them, and transpile my JavaScript with Babel before shipping it to production.

https://caniuse.com/#feat=arrow-functions

Please

Don’t use arrows as syntastic sugar, especially when you haven’t read the doc.

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