Question 203923 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – What Is the Code for One-Liner Arrow Functions That Do Not Return Any Value?

I am looking for a way to code one-liner arrow functions that do not return any value. For example:

    const fun = x => {
      console.log(x);
    };

I would remove the curly braces. Is it possible?

Tags:

4

Answers


  1. 0

    You can do it by using the void operator

    This can be used if you want to run side effect without returning the value

    For example:

    const sideEffectAndReturn = () => {
  console.log('side effect')

  return 10
}

const voidFunc = () => void sideEffectAndReturn()

const returnValue = voidFunc()

console.log({
  returnValue
})

    voidFunc will always return undefined and the side effect will still be called without the curly braces

    Login or Signup to reply.
  2. 0

    without curly braces it will be return the value

    const fun = x => x;
console.log(fun(1));

    with curly brace need to add return

    const fun1 = x => {
  return x;
};
console.log(fun1(2));
    Login or Signup to reply.
  3. 0

    Sure, just remove the braces, since console.log does not return anything itself:

    const fun = x => console.log(x);

    The result is undefined, just as with the braces and no return statement.

    If you have a single-expression body whose result value you want to suppress, you can also use the void operator:

    const fun = x => void console.log(x);
    Login or Signup to reply.
  4. 0

    If you want to be funky you can have several statements in your arrow function without braces:

    • join your statements with +. all of your statements will be executed since + doesn’t care about the operands (I sometimes use + for a couple of small statements when the return value isn’t important).
    • in the end you could have any result, add - 'x' to have it NaN
    • add || undefined to return undefined explicitly that would be equal to returning no value

    Again that’s crazy, just for stackoverflow snippet one-liners only 🙂

    const func = x => console.log('creating DIV with text:', x) + (document.body.appendChild(document.createElement('div')).textContent = x) - 'x' || undefined;

console.log(func('some test text'));

    You could use void, looks cleaner, but I don’t like extra braces:

    const func = x => void (console.log('creating DIV with text:', x) + (document.body.appendChild(document.createElement('div')).textContent = x));

console.log(func('some test text'));
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search