You can also use rest parameters:

function Numbers(...numbers){
    this.numbers = numbers;
}

When you prefixed last parameter in a function with ... it becomes rest parameter, which will cause all remaining parameters to be placed within a standard JavaScript array.

allowedFields in the below code becomes rest parameter which allows a function to accept an indefinite number of arguments as an array.

const filteredObj = (obj, ...allowedFields) => {
  const newObj = {};
  Object.keys(obj).forEach((el) => {
    if (allowedFields.includes(el)) {
      newObj[el] = obj[el];
    }
  });

  return newObj;
};

Although the other answers are correct, they change the function signature to accept an object instead of 2 separate arguments. Here is how to use an object's values as function arguments without altering the function's signature. This requires Object.values (ES 2017) and the spread operator to be available in your runtime.

const args = {
  a: 1,
  b: 2
}

const fn = (a, b) => a + b

fn(...Object.values(args));

Keep in mind this will work only in your specific case, since Object.values returns the values of all object keys and doesn't guarantee alphabetical sort order. If you want to take only the values of properties which are named a and b, you can map over Object.keys(args) and filter only those values.