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Issue #270  (Arrow Functions, Uncats, Frameworks, React)09/20/18

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There are a number of different quirks related to arrow functions in ES6. My feeling around arrow functions is that they're best used in simple examples where you're not too concerned about the value of this in a particular scope. I'll get to some of the quirks in other tips, but I thought in this tip I'll just introduce some common ways you'll see arrow function syntax expressed.

Here's the simplest example:

let myFunc = value => value;

console.log(myFunc('Hi')); // "Hi"

Try it on JS Bin

When passing a single argument to the arrow function, you can omit the parentheses around the arguments. In this case, I'm passing in a single argument, value.

Also, since there is only a single line in the function body (in this case, just a reference to the value argument), there's no need for the return keyword or curly braces around the function body. Both are implied, and the function will return whatever is evaluated in the body.

So the above would be more or less equivalent to:

var myFunc = function myFunc(value) {
  return value;

console.log(myFunc('Hi')); // "Hi"

Being so accustomed to writing ES5, I have to admit I find this much more readable (and this is what you'd get if you converted the previous snippet into ES5 using a tool like Babel). Not seeing the return keyword in there seems more confusing than it should be at first glance. It also seems more elegant with the inclusion of the word "function".

The next example is much better because it uses multiple arguments and the function body consists of two lines:

let myFunc = (a, b) => {
  a = a - 1;
  return a + b;

console.log(myFunc(4, 5)); // 8

Try on JS Bin

This is a much more readable example. The parentheses clearly indicate the arguments received and the function body is much more understandable, especially with the use of the return keyword (which is required in this instance since there are multiple expressions in the body).

If you are defining an arrow function that has no arguments, then you have to include a set of empty parentheses, like this:

let myFunc = () => 2 + 3;

console.log(myFunc()); // 5

Try on JS Bin

This arrow function receives no arguments and simply returns the lone expression's evaluation. No return keyword and no curly braces, just like the first example.

That's arrow functions in a nutshell, and I've only scratched the surface since I haven't even begun to describe any of the quirks and gotchas associated with them when used in more complex situations.

Now on to this week's tools!  

Did you enjoy this week's coding tip? Previous tips are compiled in my e-books:
► JavaScript & DOM Tips Volume 1
► JavaScript & DOM Tips Volume 2


The Uncategorizables

Getting the most out of MongoDB on AWS
In this webinar, we will introduce you to the options for deploying, managing, and optimizing MongoDB on AWS. We will also provide various tips to ensure your deployments are configured for optimal security, HA, and query performance.   sponsored via Paved 

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