Default function parameters

Question

Hi I have to admit that I am still grasping many ES6 syntax even though I have used a fair amount of them. For example, I understand that you can do console.log(multiply(5)) to get the result of a given function of

function multiply(a, b = 1) {
  return a * b;
}

But let say you have

function multiply(a, b = 1, c) {
  return a * b * c;
}

Obviously you can't do (console.log(multiply(5,,5)). In this case, is rearranging the arguments position in the function to become function multiply(a, c, b = 1) the only possible way? Or is there any other smarter way?

Answer 1

您可以传递undefined使用默认值：

function multiply(a, b = 1, c) {
  return a * b * c;
}

multiply(2, undefined, 3); // 6

您可以阅读有关默认参数值的信息，并在MDN上查看更多示例

Answer 2

Another option is to pass a single object with default property assignment instead of multiple separate arguments:

function multiply({ a, b = 1, c }) {
  return a * b * c;
}

console.log(multiply({
  a: 3,
  b: 4,
  c: 5
}));
console.log(multiply({
  a: 3,
  c: 5
}));