When to use () after a callback function name? [duplicate]

Answer 1

The difference is between passing function reference and calling that function.

The first case (probably correct) means: call this function when event occurs.

The second will be interpreted as: call this function immediately and use whatever was returned as a callback. It'll better be a function that I can call later.

The latter case will only work if the function is defined as follows:

function anotherFunction() {
    return function() {
        //real handler
    }
}