Different between normal function and arrow function: arguments not defined return an error

Question

ES6 NEWBY

I'm new to es6 and I have a problem with the arrow function that I wasn't able to resolve or find anywhere.

Here's my problem, let's take this function as a reference:

Javascript:

const plus = function() {
    let sum = 0;
    for (let i = arguments.length - 1; i >= 0; i--) {
        sum += arguments[i];
        console.log(i);
    }
    return sum;
    console.log(arguments);
}

console.log(plus(2,4,6,8));

It works fine, the result is gonna be 20, and the browser is able to interpret it. The only problem is that when I try to translate in es6, the function will return an error, in this case, arguments is not defined:

const plus = () => {
    let sum = 0;
    for (let i = arguments.length - 1; i >= 0; i--) {
        sum += arguments[i];
        console.log(i);
    }
    return sum;
    console.log(arguments);
}

console.log(plus(2,4,6,8));

I get that part, but even if I define arguments as an empty array, the result will be still the same.

I'm trying to understand the error, but not like how to solve it, the theory behind to better use es6.

Thanks

An arrow function doesn't get an `arguments` object. You can use explicit spread syntax to capture the actual arguments in an array. — Pointy, Dec 03 '19 at 14:12
Also [the MDN documentation explains this and other important differences.](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions) — Pointy, Dec 03 '19 at 14:13

score 1 · Accepted Answer · answered Dec 03 '19 at 14:14

1

Use the Spread_syntax :

const plus = (...arguments) => {
  let sum = 0;
  for (let i = arguments.length - 1; i >= 0; i--) {
    sum += arguments[i];
    // console.log(i);
  }
  // console.log(arguments);
  return sum;
}

console.log(plus(2, 4, 6, 8));

answered Dec 03 '19 at 14:14

Taki

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Do I need to explicit the parameter? Or is there another way to avoid that. The spread syntax is the way to go – Porcellino80 Dec 03 '19 at 14:15
1

yes you do need to explicit the parameter – Taki Dec 03 '19 at 14:17
const plus = (...arguments). In this case, I'm using arguments (it is a little bit confusing the name that I chose) as a parameter. Do I really need to use a parameter? – Porcellino80 Dec 03 '19 at 14:17
1

Ok, I got it and the concept of the rest parameter, thanks – Porcellino80 Dec 03 '19 at 14:19
Using `arguments` as the example name seems like a bad idea. It's also not valid in strict-mode code. Probably worth changing to `args`? – loganfsmyth Dec 04 '19 at 01:44

Different between normal function and arrow function: arguments not defined return an error

1 Answers1