The void operator evaluates its argument and always returns undefined. void allows using any expression
where an undefined is expected. However, using void makes code more difficult to understand, as the intent is often
unclear.
if (parameter === void 42) { // Noncompliant
// ...
}
doSomethingElse(void doSomething()); // Noncompliant
Instead of using void to get the undefined value, use the undefined global property. In ECMAScript5 and
newer environments, undefined cannot be reassigned. In other cases, remove the void operator to avoid confusion for
maintainers.
if (parameter === undefined) {
// ...
}
doSomething();
doSomethingElse();
Exceptions
-
void 0 (or the equivalent void(0)) is allowed as it was a conventional way to obtain the undefined value
in environments before ECMAScript 5.
if (parameter === void 0) {
// ...
}
-
void is allowed with immediately invoked function expressions.
void function() {
// ...
}();
const runPromise = () => Promise.resolve();
void runPromise();
