function doSomething(arg1){function doSomething (arg1)
 10;
// Set arg1-10 as the default, if it isn't already.
Return arg1
}
let foo = 10;
foo ===10 && doSomething()
// is the same as "foo == 10") then doSomething()
// Output: 10.
 doSomething();
// is the same as "foo!= 5" then doSomething()
// Output: 10.