In JavaScript, does it make a difference if I call a function with parentheses?

Question

I noticed a difference when calling a function with empty parentheses, or without any parentheses at all. However, I am not passing any arguments to the function so I wonder

Answer 1

Functions in javascript are first-class citizens, and as such, can be assigned to other variables or passed around as arguments.

So, when you do

window.onload = initAll;

You are setting the onload property of the window object to reference the initAll function itself.

When you do

window.onload = initAll();

You are setting the onload property to hold the return value of initAll, since it will execute in place on that line.