Evaluate multipe javascript and show text in different label or global variable from webview

1 : I put text in textbox in website.
2: I clicked button that below in textbox in website.
3: get text from a label from website.
4: get image from website.
5: click another button.
Basically i want to create youtube video downloader app using a website with evaluate javascript in webview

i don’t want to publish this app in playstore but i just want to learn something new with javascript.
Please help me

Are you sure you want to use webview as you can execute by playing with some APIs , some of them would might be free

Is there anyway to make video downloader without webview ? I don’t know …
And how to make with api