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 JavaScript and the DOM (Retiring) Responding to User Interaction Delaying Execution with setTimeout()

Posted by Shyam Gupta
Shyam Gupta
7,757 Points

How is this function executing when it's not being called? Isnt the code just a function declaration?

How is this function executing when it's not being called? Isnt the code just a function declaration?

Barry Ort
Barry Ort
12,373 Points

can you supply your code?

Shyam Gupta
Shyam Gupta
7,757 Points 
window.setTimeout((a_string) => {
console.log(a_string);

},2000,'Hello');

1 Answer

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

You're right, the function being declared as an argument to setTimeout isn't being called right now. This type of argument is know as a "callback" function. The setTimeout function saves it and then calls it later (in this case, after 2 seconds).

Sumeet Kumar
Sumeet Kumar
908 Points

How the function parameter (a_string) takes "hello" as its value