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Accept any numbers of parameters

Written byPhuoc Nguyen
01 Mar, 2021
In the old days, we can use the `arguments` variable to get the dynamic parameters that are passed to a function.
const sum = function () {
return Array.from(arguments).reduce((a, b) => a + b, 0);

sum(1); // 1
sum(1, 2); // 3
sum(1, 2, 3); // 6
sum(1, 2, 3, 4); // 10
However, most of us aren't aware about the existence of `arguments`. It has some drawbacks such as
  • It's not an array, so we usually have to convert it to array first in order to use `Array` methods
  • More importantly, it isn't available in arrow functions
The ES6 rest parameter (`...`) provides an easier way to work with an unknown numbers of parameters. The `sum` function above can be written as following:
const sum = (...params) => params.reduce((a, b) => a + b, 0);

sum(1, 2, 3, 4, 5); // 15

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Phước Nguyễn