Can Someone Help How To Create Animation In JavaScript Like Opacity

Question

I Know How To Create Like Moving object But How To Like Opacity

Sorry My English Is bad :')

Answer 1

Do the same with its positions when making a moving objects, but make it change the opacity, and make it between 0 and 1

Answer 2

See my code:
https://code.sololearn.com/W9NOTx6Vj8xa/#html

Answer 3

Bonjour, ça fait 2 jours j’essaie de comprendre cette formule: else {
pos + = 1;
box.style.left = pos + "px";
et j'arrive pas à comprendre.
pourquoi pas + -1
pourquoi left=pas +px ???

Answer 4

Thank You All