void.md

What does void do?

The void operator evaluates the given expression and then returns undefined.

Description

This operator allows inserting expressions that produce side effects 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 instead (assuming it has not been assigned to a non-default value).

Immediately Invoked Function Expressions

When using an immediately-invoked function expression, void can be used to force the function keyword to be treated as an expression instead of a declaration.

void function iife() {
    var bar = function () {};
    var baz = function () {};
    var foo = function () {
        bar();
        baz();
     };
    var biz = function () {};

    foo();
    biz();
}();

JavaScript URIs When a browser follows a javascript: URI, it evaluates the code in the URI and then replaces the contents of the page with the returned value, unless the returned value is undefined. The void operator can be used to return undefined. For example:

<a href="javascript:void(0);">
  Click here to do nothing
</a>

<a href="javascript:void(document.body.style.backgroundColor='green');">
  Click here for green background
</a>

Note, however, that the javascript: pseudo protocol is discouraged over other alternatives, such as unobtrusive event handlers.