Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript Callback Functions in JavaScript Introduction to Callback Functions Creating an Anonymous Callback Function

Posted by Leslio McKeown
.a{fill-rule:evenodd;}techdegree
Leslio McKeown
Python Development Techdegree Student 9,390 Points

I don't understand what it is asking me

I don't know how to execute the app.js and I keep getting an error in the runner.js when I put

runner.js functionRunner(function() { console.log("Hello World!"); });

app.js 
function log() {

}
index.html 
<!DOCTYPE html>
<html lang="en">
    <head>
        <title></title>
        <link rel='stylesheet' href='styles.css'>
    </head>
    <body>
        <section>
            <p>Open your browser's console to see the results</p>
        </section>
        <script src='runner.js'></script>
        <script src='app.js'></script>
    </body>
</html>
runner.js 
functionRunner(function() {
  console.log("Hello World!");
});

1 Answer

Daniel Turato
seal-mask
PLUS
.a{fill-rule:evenodd;}techdegree seal-36
Daniel Turato
Java Web Development Techdegree Graduate 30,124 Points
Daniel Turato
.a{fill-rule:evenodd;}techdegree seal-36
Daniel Turato
Java Web Development Techdegree Graduate 30,124 Points

You have to do this:

functionRunner(() => {
    console.log("Hello World!");
});

This basically is an anonymous function with the () means no parameters and the body being a normal function. You use the arrow '=>' to create such a function.

You can read more about it here - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

Leslio McKeown
.a{fill-rule:evenodd;}techdegree
Leslio McKeown
Python Development Techdegree Student 9,390 Points

Thank you very much for your help, and thanks for the link that you sent.