How to create or modify the 'onclick' event of an HTML element from js?

Question

Hi everyone!!
I'm very clear how to create and add an HTML element from js.
window.onload = function() {
//creating a new button
var b = document.createElement("button");
var node = document.createTextNode("button");
//adding the text to the button
b.appendChild(node);
var div = document.getElementById("demo");
//adding the button to the div
div.appendChild(b);
};
https://www.sololearn.com/learn/JavaScript/2755/
Now ... how do I add or modify the 'onclick' event or any other parameter to it?

Answer 1

b.addEventListener("click", function(e){
//stuff to be done
});
(you can also give a function name as parameter, that function then will be called)

Answer 2

But if you already have an onclick event, and want to modify it, you could use:
element.onclick = function() {};
(Although addEventListener is better)

Answer 3

All elements have a style object, so you can do:
document.querySelector("button").style["background-color"] = "blue";
And, some attributes can be accessed directly, like the class, as:
element.className = "btn-class";

Answer 4

Thanks Anton and Airree. But there is a new question 😀.
That's in events case, how it would be to add the online style??
Ex: <button style="background-color:blue; color: #fff;"> Button </button>
Or Its own class??
Ex: <button class="btn-class"> Button </button>

Answer 5

I get it, thanks a lot Airree