why params in javascript code example

Example 1: javascript function variable arguments

function foo() {
  for (var i = 0; i < arguments.length; i++) {
    console.log(arguments[i]);
  }
}

foo(1,2,3);
//1
//2
//3

Example 2: javascript function multiple parameters

function sum(...values) {
    console.log(values);
}
sum(1);
sum(1, 2);
sum(1, 2, 3);
sum(1, 2, 3, 4);


function sum(...values) {
    let sum = 0;
    for (let i = 0; i < values.length; i++) {
        sum += values[i];
    }
  
    return sum;
}
console.log(sum(1)); //1
console.log(sum(1, 2)); //3
console.log(sum(1, 2, 3)); // 5
console.log(sum(1, 2, 3, 4)); //10