/frontend-react-best-practices

Preload Based on User Intent

Preload heavy bundles before they're needed to reduce perceived latency.

Example (preload on hover/focus):

function EditorButton({ onClick }: { onClick: () => void }) {
  let preload = () => {
    if (typeof window !== "undefined") {
      void import("./monaco-editor");
    }
  };

  return (
    <button onMouseEnter={preload} onFocus={preload} onClick={onClick}>
      Open Editor
    </button>
  );
}

Example (preload when feature flag is enabled):

function FlagsProvider({ children, flags }: Props) {
  useEffect(() => {
    if (flags.editorEnabled && typeof window !== "undefined") {
      void import("./monaco-editor").then((mod) => mod.init());
    }
  }, [flags.editorEnabled]);

  return (
    <FlagsContext.Provider value={flags}>{children}</FlagsContext.Provider>
  );
}

The typeof window !== 'undefined' check prevents bundling preloaded modules for SSR, optimizing server bundle size and build speed.