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JavaScript Callback Functions in JavaScript Callbacks and the DOM Callbacks with DOM Elements

Posted by Zak Mosbacher
.a{fill-rule:evenodd;}techdegree seal-36
Zak Mosbacher
Full Stack JavaScript Techdegree Graduate 16,080 Points

There was an error with your code: TypeError: 'undefined' is not an object (evaluating 'event.target.className = "spin"'

Am i supposed to add a specific thing to the parameter in the event listener?, thanks for the help

app.js 
const btn1 = document.getElementById("button1");
const btn2 = document.getElementById("button2");
const btn3 = document.getElementById("button3");

function spinElement(event) {
  //Applies spinning animation to button element
  event.target.className = "spin";
}
btn1.addEventListener('click', spinElement())
btn2.addEventListener('click', spinElement())
btn3.addEventListener('click', spinElement())
index.html 
<!DOCTYPE html>
<html lang="en">
    <head>
        <title></title>
        <link rel='stylesheet' href='styles.css'>
    </head>
    <body>
        <section >
            <button id='button1'>Button 1</button>
            <button id='button2'>Button 2</button>
            <button id='button3'>Button 3</button>
        </section>
        <script src='app.js'></script>
    </body>
</html>

1 Answer

Dave StSomeWhere
Dave StSomeWhere
19,870 Points
Dave StSomeWhere
Dave StSomeWhere
19,870 Points

Your callback function in the eventlistener should not have parenthesis.

btn1.addEventListener('click', spinElement())  // bad
btn1.addEventListener('click', spinElement)  // good
Zak Mosbacher
.a{fill-rule:evenodd;}techdegree seal-36
Zak Mosbacher
Full Stack JavaScript Techdegree Graduate 16,080 Points

Thank you!