return;return expression;

expressionOptional

The expression whose value is to be returned. If omitted,undefined is returned.

Thereturn statement can only be used within function bodies. When areturn statement is used in a function body, the execution of the function is stopped. Thereturn statement has different effects when placed in different functions:

• In a plain function, the call to that function evaluates to the return value.
• In an async function, the produced promise is resolved with the returned value.
• In a generator function, the produced generator object'snext() method returns{ done: true, value: returnedValue }.
• In an async generator function, the produced async generator object'snext() method returns a promise fulfilled with{ done: true, value: returnedValue }.

If areturn statement is executed within atry block, itsfinally block, if present, is first executed, before the value is actually returned.

The syntax forbids line terminators between thereturn keyword and the expression to be returned.

returna + b;

The code above is transformed byautomatic semicolon insertion (ASI) into:

return;a + b;

This makes the function returnundefined and thea + b expression is never evaluated. This may generatea warning in the console.

To avoid this problem (to prevent ASI), you could use parentheses:

return (  a + b);

A function immediately stops at the point wherereturn is called.

function counter() {  // Infinite loop  for (let count = 1; ; count++) {    console.log(`${count}A`); // Until 5    if (count === 5) {      return;    }    console.log(`${count}B`); // Until 4  }  console.log(`${count}C`); // Never appears}counter();// Logs:// 1A// 1B// 2A// 2B// 3A// 3B// 4A// 4B// 5A

See also the article aboutClosures.

function magic() {  return function calc(x) {    return x * 42;  };}const answer = magic();answer(1337); // 56154

• Functions
• Closures