Button value output in console.log with JS

I’m fairly new to HTML and JS. I need the value of my HTML button to show in the console.log with JS. I dont want to use onclick=”…” though.

This is part of my HTML file:

<button id="kaufknopf" value="4,50">4,50€</button>

This is my JS file:

function output() {
    console.log(price);
}

var price = document.getElementById("kaufknopf").value;
price.addEventListener("click", output, true);

Answer

1) You have to add event listener on the html element not on the value of that element.

var price = document.getElementById( "kaufknopf" );
price.addEventListener( "click", output, true );

2) After you click on the button you have to grab its value using price.value

function output() {
  console.log( price.value );
}

function output() {
  console.log(price.value);
}

var price = document.getElementById("kaufknopf");
price.addEventListener("click", output, true);

<button id="kaufknopf" value="4,50">4,50€</button>