Portals

Modals are a common UI pattern but can be tricky to implement correctly due to CSS stacking contexts and z-index issues. React, Angular, and Vue all provide a Portals API specifically designed to solve this problem by rendering components outside their normal DOM hierarchy. The post walks through building a modal component in all three frameworks, demonstrates the CSS stacking context problem, and shows how portals resolve it by teleporting rendered output to a different DOM node.