Question

Aside from the obvious preventing of links being clicked (with javascript:void(0);) and for the definition of undefined in many javascript precompiled languages like coffeescript (where undefined becomes void 0) –> What else can the void function be used for?

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Related: What does "javascript:void(0)" mean?

Useful Link: MDN page for void

Answer 1

First, void is an operator, not a function. The answer to your question can’t be given any more clearly than the explanation given in the link to MDN you provided in your question:

Summary

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

…

Uses

This operator allows inserting expressions that produce side effects into places where an expression that evaluates to undefined is desired.

Theoretical use:

Change the return value of an expression that produces side effects.

var i;
i = 0;       // returns 0
void i = 1;  // returns undefined

But this use is not very valuable in most situations.

Practical uses:

We already know about:

• Cancel navigation in a bookmarklet
• Compare item to undefined – Since the global variable undefined could be modified (it is not a reserved word), void 0 is a more reliable way to get an undefined value. Eg: obj.foo === void 0

Other uses:

Prevent verbose console output – I use it in a JavaScript console when I only want to execute some code and don’t want to pollute the console with uninteresting verbose output.

Explicitly pass undefined to a function – It can be useful to know whether a function was called without passing arguments, or whether an argument was passed to a function with a value of undefined:

function countArguments(a) {
    console.log(a === undefined);
    console.log(arguments.length);
}
countArguments();
countArguments(void 0);

Your console output would be:

true
0
true
1

Does JavaScript need this operator? Probably not. You can get the same functionality (and more) from a self invoking anonymous function:

(function(){ /* expression */ })()

But that’s not quite as concise.