Javascript:如何编写接受不同数量参数的函数

function sum() {
  var total = 0;
  for (var i = 0; i < arguments.length; i++) {
    total += arguments[i];
  }
  return total;
}

console.log(sum(1, 2, 3)); // 输出 6
console.log(sum(1, 2, 3, 4, 5)); // 输出 15

function sum(...numbers) {
  var total = 0;
  for (var i = 0; i < numbers.length; i++) {
    total += numbers[i];
  }
  return total;
}

console.log(sum(1, 2, 3)); // 输出 6
console.log(sum(1, 2, 3, 4, 5)); // 输出 15

function sum(a = 0, b = 0, c = 0) {
  return a + b + c;
}

console.log(sum(1, 2, 3)); // 输出 6
console.log(sum(1, 2)); // 输出 3
console.log(sum(1)); // 输出 1
console.log(sum()); // 输出 0