void Keyword

This operator allows evaluating expressions that produce a value into places where an expression that evaluates to undefined is desired.

The void operator is often used merely to obtain the undefined primitive value, usually using void(0) (which is equivalent to void 0). In these cases, the global variable undefined can be used.

It should be noted that the precedence of the void operator should be taken into account and that parentheses can help clarify the resolution of the expression following the void operator:

void 2 === '2';   // (void 2) === '2', returns false
void (2 === '2'); // void (2 === '2'), returns undefined