Difference Between Countup() And Countup

I have a script that counts up the number in a box (actually, in this exercise -> http://jqexercise.droppages.com/#page_0022_ ) each 1 second like this. var target = $('#target

Solution 1:

countUp references the function as an object. In JavaScript everything is an object, including functions, and can be passed around. countUp() calls the function countUp and returns its value.

Solution 2:

Adding the () to the function invokes it instantly, while just using the function name is actually passing it as a parameter.

Solution 3:

countUp() is a recursive invocation of the function. Each call to the function invokes it again (immediately), and the return value (which is undefined) is passed to setTimeout.

This would be an infinite loop, except I believe the exception from setTimeout receiving a non function is interrupting it after 1 second, leading to a stop at 15616.