What is the meaning of “foo(…arg)” (three dots in a function call)?

Question

Can someone tell what is \"...\" in the below code in the \"Intro to Angular\" example?

getHeroes() {
    this.backend.getAll(Hero).then( (heroes: Hero[]) =&         


        

Answer 1

It is a JavaScript feature called Rest Parameters. By using it your function can take any number of arguments. You put the three dots just before the argument (without a whitespace character) and the mechanism spreads it for you as if it was a list of several arguments. In Eloquent Javascript you have a good example of it.

let numbers = [5, 1, 7];
console.log(max(...numbers));
// -> 7