Does javascript developer have to make the layout/template of the site or do i start from a made site? Adding functionality, all the js magic? [closed]

What exactly does a dev job look like? Do i as a js developer add loops, functions, objects, control DOM or do i have to trouble myself with all those grids, floats, flexboxes? Do designers make the code for it? For me layouts seem troubling for now, especially since just making sites doesn't give you that much money. It's hard selling templates with wordpress around. Maintaining sites seems more profitable to me. I love javascript, i loved C++ just overall adding loops to a site seems easy to me, making objects which are extended variables, controlling DOM.