TypeScript Assertion Patterns

Type assertions tell TS: trust me, I know the type.

      ## Basic assertion
      ```ts
      const el = document.getElementById("app") as HTMLDivElement;
      el.innerHTML = "Hello";
      ```
      
      ## Angle bracket (not in JSX)
      ```ts
      const val = <string>someValue;
      ```
      
      ## Dangerous example
      ```ts
      const n = "hello" as unknown as number;
      ```
      
      This can break logic.
      
      ## Safer pattern: runtime check
      ```ts
      const el = document.getElementById("app");
      if (el instanceof HTMLDivElement) {
        el.innerHTML = "Safe";
      }
      ```
      
      ## Graph
      ```mermaid
      flowchart TD
        A[Unknown Value] --> B[Assertion]
        B --> C[Trusted Type]
      ```
      
      ## Remember
      - Assertions bypass checks
      - Prefer type guards first
      - Use only when you are sure