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
Hamzah Iqbal
Full Stack JavaScript Techdegree Student 11,145 PointsWhat is the purpose of the () => getJSON, as in why does it need the () ?
I understrøms that one is pasning in the function but what is the purpose of the ()
3 Answers
Steven Parker
231,269 PointsThe parentheses just act as a placeholder for when the function takes no arguments. They are also used when the function takes multiple arguments. The only case where they are not needed is when the function takes only one argument (in which case the parameter name would be there).
Rafic Jouejati
14,976 Pointsi get it now!! Makes sense!! I really appreciate your expertise, thanks brother!!
Steven Parker
231,269 PointsRafic Jouejati — Glad to help. You can mark a question solved by choosing a "best answer".
And happy coding!
Farid Lavizadeh
12,006 PointsUnless a named function is tied to an event, it will just run without the event occurring. Since getJSON(astrosUrl) is not tied to any event, it will run before a user clicks anything. To tie the named function to an event, a preceding anonymous function is used.
Rafic Jouejati
14,976 PointsRafic Jouejati
14,976 PointsHi Steven, thanks for your help. Can you clarify a little? I'm still confused.
not sure why it is: btn.addEventListener('click', () => getJSON(astrosUrl));
instead of btn.addEventListener('click', getJSON(astrosUrl));
why do you have to add the anonymous function () =>
Thank you so much!
Steven Parker
231,269 PointsSteven Parker
231,269 PointsThe anonymous function will run when the event occurs. It will run the "getJSON" at that time.
If you don't create the function, it will run "getJSON" now instead, plus it will expect it to return a function to be used as a callback when the event does happen.