Creating Generic Javascript Functions (ie. El.onmouseclick = Function ...)

I want to learn more about creating functions for element events
without having to put onclick event in every tag. For example:

<script>
document.getElementsByTagName('input').onclick = function () {
alert('hello');
}
</script>

Now, I know the above does not work as I have tried it but hopefully
the idea of what I am trying to achieve here. Basically for every input
tag, when the user triggers the event (click) it will do the same
function.

Anyway, I would more so like to learn about this type of scripting
where you assign functions to events. However, I dont know what to
search for in google and the like. Where could I learn more about this?