rest parameters

function f(a, b, ...theArgs) {
  // ...
}

// Before rest parameters, the following could be found:
function f(a, b) {
  var args = Array.prototype.slice.call(arguments, f.length);

  // ¡­
}

// to be equivalent of

function f(a, b, ...args) {
  
}

function f(...[a, b, c]) {
  return a + b + c;
}

f(1)          // NaN (b and c are undefined)
f(1, 2, 3)    // 6
f(1, 2, 3, 4) // 6 (the fourth parameter is not destructured)

function fun1(...theArgs) {
  console.log(theArgs.length);
}

fun1();  // 0
fun1(5); // 1
fun1(5, 6, 7); // 3

function multiply(multiplier, ...theArgs) {
  return theArgs.map(function(element) {
    return multiplier * element;
  });
}

var arr = multiply(2, 1, 2, 3); 
console.log(arr); // [2, 4, 6]

function sortRestArgs(...theArgs) {
  var sortedArgs = theArgs.sort();
  return sortedArgs;
}

console.log(sortRestArgs(5, 3, 7, 1)); // shows 1, 3, 5, 7

function sortArguments() {
  var sortedArgs = arguments.sort(); 
  return sortedArgs; // this will never happen
}

// throws a TypeError: arguments.sort is not a function
console.log(sortArguments(5, 3, 7, 1));

function sortArguments() {
  var args = Array.prototype.slice.call(arguments);
? var sortedArgs = args.sort();
? return sortedArgs;
}
console.log(sortArguments(5, 3, 7, 1)); // shows 1, 3, 5, 7