Why does void in Javascript require an argument?

Question

From what I understand, the keyword void in Javascript is some kind of function that takes one argument and always returns the undefined value. For

Answer 1

void also evaluates the expression you pass to it. It doesn't just return undefined.

Answer 2

As per this page https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/void void is an operator, which simply returns undefined, after evaluating the expression you pass to it. An operator needs an operand to operate on. That is why pass a parameter.

console.log(void true);
console.log(void 0);
console.log(void "Welcome");
console.log(void(true));
console.log(void(0));
console.log(void("Welcome"));

All these statements would print undefined

var a = 1, b = 2;
void(a = a + b)
console.log(a);

And this would print 3. So, it is evident that, it evaluates the expressions we pass to it.

Edit: As I learn from this answer https://stackoverflow.com/a/7452352/1903116

undefined is just a global property which can be written to. For example,

console.log(undefined);
var undefined = 1;
console.log(undefined);

It prints

undefined
1

So, if you want to absolutely make sure that the undefined is used, you can use void operator. As it is an operator, it cannot be overridden in javascript.