How to return null value in Javascript function

Question

Question Noob. Learning Javascript functions and the problem with the problem below.

Modify this function so that if it is called with 1 or 0 arguments, it returns null.

function divide(num1, num2) {
    return num1 / num2;
}
let num1 = null;
let num2 = null;
let answer = divide(1,1)
console.log(answer);

Thank!

Answer 1

TL DR

Assuming we only need to apply direct change, I would avoid too syntactic sugar and simply write it like this:

function divide(num1, num2) {
  if (arguments.length < 2) {
    return null;
  }
  return num1/num2;
}

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If we want to make it simple and elegant, I would write it this way (this requires ES6 functions):

const divide = (...args) => args.length < 2 ? null : args[0] / args[1];

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Description

Improvement Steps in Vanilla JS (ES5 and earlier)

• : , , , , .

function divide(num1, num2) {
  if (arguments.length < 2) {
    return null;
  }
  return num1/num2;
}

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, , arguments, .

• ** ** , ?, if statement

function divide(num1,num2) {
  return arguments.length < 2 ? null : num1 / num2;
}

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ES6

• ( rest): ... , , , .

function divide(...args) {
  return args.length < 2 ? null : args[0] / args[1];
}

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JavaScript , , args. , , args.

• : , , , , .

const divide = (...args) => args.length < 2 ? null : args[0] / args[1];

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, , , , - undefined , 2 , , NaN, 2.

function divide(num1, num2) {
	  if (num1 === undefined || num2 === undefined) {
return null;
  }
  return num1/num2;
}

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function divide1(num1, num2) {
	  if (arguments.length < 2) {
	    return null;
	  }
	  return num1/num2;
	}
	
function divide2(num1,num2) {
	  return arguments.length < 2 ? null : num1 / num2;
	}
	
	
function divide3(...args) {
	  return args.length < 2 ? null : args[0] / args[1];
	}


const divide4 = (...args) => args.length < 2 ? null : args[0] / args[1];


const test = (cb) => {
  console.log("-------->" + cb.name)
  console.log(cb());
  console.log(cb(1));
  console.log(cb(1, 2));
  console.log(cb(1, undefined));
  console.log(cb(1, null));
  console.log(cb(1, 2, 3));
};

test(divide1);
test(divide2);
test(divide3);
test(divide4);

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Answer 2

.

function divide(num1, num2) {
    if(arguments.length < 2) return null;
    return num1 / num2;
}

arguments (-) , . length, , .

Answer 3

Technically, passing to null will call it with two arguments, so your example doesn't exactly represent this. If you need an answer that is safe for arrow functions (they don't have an object arguments), you can simply check if the second argument is a number. It will catch a lot.

function divide(num1, num2) {
    if (typeof num2 !== 'number') return null;
    return num1 / num2;
}

If you want to handle the edge when the first argument passed was undefined, you can check both arguments.

function divide(num1, num2) {
    if (typeof num1 !== 'number' || typeof num2 !== 'number') return null;
    return num1 / num2;
}

If you want a fantasy, it could be a single line arrow:

const divide = (num1, num2) => typeof num2 !== 'number' ? null : num1 / num 2;