Rest Parameters in ES6

Question

what does these following lines mean?

function containsAll(arr) {
for (let k = 1; k < arguments.length; k++) {
let num = arguments[k];
if (arr.indexOf(num) === -1) {
return false;
}
}
return true;
}

let x = [2, 4, 6, 7];
console.log(containsAll(x, 2, 4, 7));
console.log(containsAll(x, 6, 4, 9));

please can anyone explain me this code?

Answer 1

`arguments` is like an array and it contains all arguments passed to your function. For example if you have

something(x, 2, 4, 7);

then

arguments[0] == x
arguments[1] == 2
arguments[2] == 4
arguments[3] == 7

However, this is not nice ES6 code. In ES6 we should to do this instead:

function containsAll(arr, ...rest) {
for(let num of rest) {
if(arr.indexOf(num) === -1)
return false;
}
return true;
}