Intro to JavaScript Functions Advanced Arrow Functions

Learning Objective: By the end of this lesson, students will be able to optimize arrow functions through the use of implicit returns and single parameter syntax, while understanding the limitations associated with the this keyword.

Implicit return

Arrow functions composed of a single expression (something resolves to a single value) will automatically evaluate and return that expression without requiring us to write the return keyword. Just leave off the curly braces, and the rest happens automatically.

const multiply = (numA, numB) => numA * numB;

console.log(multiply(3, 4));
// Prints: 12

Single parameters

When working with a single parameter, we can omit the parentheses entirely:

// note the lack of () around the num parameter!
const addTwo = num => {
  console.log(num + 2);
}

addOne(2);

Combining these ideas

Here’s an example combining both of the above concepts and using them in a single function:

const double = num => num * 2;

Arrow function pitfalls

Arrow Functions have a unique way of binding the this keyword, which makes them unsuitable for use as object methods or constructors - but don’t worry too much about that for now.