Função

function addition(param1, param2) {
  return param1 + param2;
}
 
console.log(addition(1)); //=> NaN
console.log(addition(1, 2)); //=> 3
console.log(addition(1, 2, 3)); //=> 3

function addition(param1, param2) {
  return param1 + param2;
}
 
console.log(addition(1)); //=> NaN
console.log(addition(1, 2)); //=> 3
console.log(addition(1, 2, 3)); //=> 3

const addition = function (param1, param2) {
  return param1 + param2;
};
 
console.log(addition(1, 2)); //=> 3

const addition = function (param1, param2) {
  return param1 + param2;
};
 
console.log(addition(1, 2)); //=> 3

const addition = (param1, param2) => {
  return param1 + param2;
};
 
console.log(addition(1, 2)); //=> 3

const addition = (param1, param2) => {
  return param1 + param2;
};
 
console.log(addition(1, 2)); //=> 3

const addition = (param1, param2) => param1 + param2;
 
console.log(addition(1, 2)); //=> 3

const addition = (param1, param2) => param1 + param2;
 
console.log(addition(1, 2)); //=> 3

function addition(param1, param2) {
  return param1 + param2;
}
 
function Addition(param) {
  return param + 1;
}
 
console.log(Addition(1)); //=> 2
console.log(Addition(1, 2)); //=> 2

function addition(param1, param2) {
  return param1 + param2;
}
 
function Addition(param) {
  return param + 1;
}
 
console.log(Addition(1)); //=> 2
console.log(Addition(1, 2)); //=> 2

function addition(param1, param2) {
  return param1 + param2;
}
 
function addition(param) {
  return param + 1;
}
 
console.log(addition(1)); //=> 2
console.log(addition(1, 2)); //=> 2

function addition(param1, param2) {
  return param1 + param2;
}
 
function addition(param) {
  return param + 1;
}
 
console.log(addition(1)); //=> 2
console.log(addition(1, 2)); //=> 2

function addition(param1, param2 = 0) {
  return param1 + param2;
}
 
console.log(addition(1)); //=> 1
console.log(addition(1, 2)); //=> 3

function addition(param1, param2 = 0) {
  return param1 + param2;
}
 
console.log(addition(1)); //=> 1
console.log(addition(1, 2)); //=> 3

function addition(...params) {
  let summation = 0;
  for (let value of params) {
    summation += value;
  }
  return summation;
}
 
console.log(addition(1)); //=> 1 ([1])
console.log(addition(1, 1)); //=> 2 ([1, 1])
console.log(addition(1, 1, 1, 1)); //=> 4 ([1, 1, 1, 1])

function addition(...params) {
  let summation = 0;
  for (let value of params) {
    summation += value;
  }
  return summation;
}
 
console.log(addition(1)); //=> 1 ([1])
console.log(addition(1, 1)); //=> 2 ([1, 1])
console.log(addition(1, 1, 1, 1)); //=> 4 ([1, 1, 1, 1])

function calc(param1, param2, callback) {
  return callback(param1, param2);
}
 
console.log(calc(2, 1, (x, y) => x + y)); //=> 3
console.log(calc(2, 1, (x, y) => x - y)); //=> 1
console.log(calc(2, 1, (x, y) => x * y)); //=> 2
console.log(calc(2, 1, (x, y) => x / y)); //=> 2
console.log(calc(2, 1, (x, y) => x ** y)); //=> 2

function calc(param1, param2, callback) {
  return callback(param1, param2);
}
 
console.log(calc(2, 1, (x, y) => x + y)); //=> 3
console.log(calc(2, 1, (x, y) => x - y)); //=> 1
console.log(calc(2, 1, (x, y) => x * y)); //=> 2
console.log(calc(2, 1, (x, y) => x / y)); //=> 2
console.log(calc(2, 1, (x, y) => x ** y)); //=> 2