Hi Yann,
Yes, your $w(“#button3”).onClick ( line is wrong. Look at this documentation page:
https://www.wix.com/corvid/new-reference/$w/button/onclick
That should solve your problem.
~Hope this helps!~
Arthur 
Hi Yann,
Yes, your $w(“#button3”).onClick ( line is wrong. Look at this documentation page:
https://www.wix.com/corvid/new-reference/$w/button/onclick
That should solve your problem.
~Hope this helps!~
Arthur