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Traditional Functions or Arrow Functions in Javascript?

Jose Arteaga on October 30, 2019

Recently, I started my Web Dev journey, and these days I have been reading about functions in Javascript. I've noticed that there are many ways to ...

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Thomas Step • Oct 30 '19

The order matters. Declare it
into a variable and then call it.

I might be incorrectly interpreting what you're saying, but have you heard of IIFE? developer.mozilla.org/en-US/docs/G...
You can create a function and immediately call it while storing the result in a variable.

Jose Arteaga • Oct 30 '19

Exactly! It was more related to hoisting. I mean, there must be an error if I call the function expression before its declaration. Otherwise with traditional functions it won't happened.

By the way, thanks for the information about IIFE, I will read up on it.

Thomas Step • Oct 31 '19

I definitely misunderstood the first time through so I apologize for that.

Jose Arteaga • Oct 31 '19

There's no problem Thomas! Thank you for your response and help.

SavagePixie • Oct 30 '19

I think the author was referring to the fact that function expressions aren't hoistered.

Ed Reeseg • Oct 30 '19

I use them pretty interchangeably these days - I like the traditional syntax for how self-explanatory it is (though, these days, I think most people are just as familiar with ES6 arrow syntax).

As Ben mentioned previously, one of the main draws of arrow syntax has to do with how it interacts with the this keyword. It does not generate its own context for this, but rather inherits the context of the environment in which it was created.

For things like React class components, this can be a godsend.

class Test extends React.Component {
  constructor(props){
    this.log = this.log.bind(this);
  }
  log(){
    console.log(this);
  }
  render(){
    return // Whatever
  }
}

vs.

class Test extends React.Component {
  log = () => console.log(this);
  render(){
    return // Whatever
  }
}

Of course, with more people being familiar with the convenience of Hooks, this is a bit less relevant. Still good to note.

Jose Arteaga • Oct 30 '19

Right! I was reading more about it and I found what you mentioned about the this keyword. I'm not familiar yet with this concept, but I will read up on it. For sure there should be an advantage using the arrow syntax. Thanks Ed!

SavagePixie • Oct 30 '19 • Edited

Once you override the variable
where the function lives, it's over.

If you assign them to a constant, you don't run the risk of overriding them. In general, it's a good idea to always use the keyword const if you want to store your function expressions.

Generally I favour expressions over declarations because they are shorter to type. When written as callbacks, they also seen clearer to me.

Jose Arteaga • Oct 30 '19

Interesting! You're right! I forgot about const. That's a good one! Thanks for the advice.

Ben Calder • Oct 30 '19

This seems to be a recurring question. The most important purpose of arrow functions is actually to do with maintaining scope.

Jose Arteaga • Oct 30 '19

Thanks Ben for sharing your article! It is well-explained! I will deep into it and understand it.