How to pass the nth optional argument without passing prior arguments in JavaScript functions? [duplicate]

问题

This question already has answers here:

Is there a way to provide named parameters in a function call in JavaScript? (10 answers)

Closed 1 year ago.

So imagine we got a function like below, and I want to use the default value for the first parameter a and a custom value for second parameter b.

const func = (a = 1 , b = 2) => {
    console.log("a is equal to " + a, " and b is equal to " + b)
}

I want to just pass one value for parameter b. something like this:

func(b : 7);
// I want it to print: a is equal to 1 and b is equal to 7

How can I achieve it in JavaScript?

回答1:

You modify your function to receive an object and then inside that object you can also define default values for some properties like a and b.

const func = ({ a = 1, b = 2 }) => {
  console.log("a is equal to " + a, " and b is equal to " + b)
}

func({b: 3})

回答2:

try to use RORO pattern, to pass object into function

来源：https://stackoverflow.com/questions/57040478/how-to-pass-the-nth-optional-argument-without-passing-prior-arguments-in-javascr