Im new to ionic , some questions

Hey guys Im very new to ionic programming.

I got my first basic app running (just tested a few html elements and imported a cordova barcode scanner ) .

can i use simple html elements to make my app or do i have to use the ionic ui components ??
the ionic website advertises i can use es2015 compliant javascript to make my app …

but it seems thats not the correct way , and the uicomponents are not as nice as i thought …

my app basically just needs to read a json file and populate a list of items where i can change some properties(all easily doable with simple js/html) and then save the object as a new json-file with date attached …

the barcode scanner is used to select a specific entry in that list

i now want to add a simple function (alert/console.log) … but i dont even know where to put it , i tried to add it into “class HomePage” in but using a simple html5 select onchange=“run()” returns function not defined ,

do i have to use the ionic components or is html5 possible ?

Can you share a code on stack blitz?