Event is undefined (javascript

Question

I want to add an event manager but, it won't work?

Console shows me

"ReferenceError: event is not defined"

document.getElementsByTagName('div')[0].addEventListener("mousemove", myFunction(event));

function myFunction(event) {
    var x = event.pageX;
    var y = event.pageY;
    var coor = "Coordinates: (" + x + "," + y + ")";
    document.getElementByTagName('p')[0].textContent = coor;
}

<div> 
<p></p>
</div>

I know that now, I can't put identifiers on my code. It's for school, they want us to target the elements using getElementsByTagName... — PostMaloneM3m3r, Mar 26 '18 at 21:34

Vadym Shashkov · Accepted Answer · 2018-03-26T21:31:47.870

When you create an event listener, write the only name of the function:

element.addEventListener("mousemove", myFunction);

document.getElementsByTagName('div')[0].addEventListener("mousemove", myFunction);

function myFunction(event) {
    var x = event.pageX;
    var y = event.pageY;
    var coor = "Coordinates: (" + x + "," + y + ")";
    document.getElementsByTagName('p')[0].textContent = coor;
}

div {
  background-color: red;
  width: 200px;
  height: 200px;
}

<div>
  <p></p>
</div>

score 0 · Answer 2 · answered Mar 26 '18 at 21:21

While Vadim Shashkov is correct, there is more reasoning behind it. According to documentation put out by Mozilla (https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener) you are giving the addEventListener function a value instead of a function. You need to give it the function, which is why

document.getElementById('myDiv').addEventListener("mousemove", myFunction);

works.

Event is undefined (javascript

2 Answers2