While with a normal function you can use the arguments implicit object to see the given params:
function myFunction() {
console.log(arguments);
}
myFunction('a', 'b');
// logs { 0: 'a', 1: 'b', length: 2 }
In an arrow function this will end up with an unexpected result:
function myFunction() {
const arrowF = () => console.log(arguments);
arrowF('c', 'd');
}
myRegularFunction('a', 'b');
// will log { 0: 'a', 1: 'b', length: 2 }
// insead of the expected { 0: 'c', 1: 'd', length: 2 }
This happens because of the fact that that arrow functions don't have an arguments
object. They also don't have their own this context and therefore the arguments
is the one from the myRegularFunction
context.
However, we can use a rest parameter to spread the arguments in an arrow function:
function myRegularFunction() {
const arrowF = (...args) => console.log(args);
arrowF('c', 'd');
}
myRegularFunction('a', 'b');
// logs ['c', 'd']
And we can even make some cool stuff like combining regular parameters with a rest parameter:
function multiplyTheSum(multiplier, ...numbers) {
console.log(multiplier); // 2
console.log(numbers); // [10, 20, 30]
const sum = numbers.reduce((s, n) => s + n);
return multiplier * sum;
}
multiplyTheSum(2, 10, 20, 30); // => 120
Btw, if you are interested you can read more also about the function declarations vs the function expressions and when it's best to use a regular function instead of an arrow function.
📖 50 Javascript, React and NextJs Projects
Learn by doing with this FREE ebook! Not sure what to build? Dive in with 50 projects with project briefs and wireframes! Choose from 8 project categories and get started right away.
📖 50 Javascript, React and NextJs Projects
Learn by doing with this FREE ebook! Not sure what to build? Dive in with 50 projects with project briefs and wireframes! Choose from 8 project categories and get started right away.