타입 어서션 & Non-null 어서션

// as 타입 어서션 시뮬레이션
  const unknownData = 'T-800';
  const asString = unknownData;  // (unknownData as string)
  const asNumber = Number(unknownData.replace(/[^0-9]/g, ''));  // (unknownData as unknown as number)

  // DOM Non-null 어서션
  const container = document.currentScript.parentElement;  // document.getElementById('app')!

  // 이중 어서션
  function forceType(val) { return val; }  // val as unknown as TargetType

  const results = [
    { desc: 'as string 어서션', result: `"${asString}" (${typeof asString})`, safe: true },
    { desc: 'as number 변환', result: `${asNumber} (${typeof asNumber})`, safe: true },
    { desc: 'Non-null ! 어서션', result: container ? 'DOM 요소 있음 ✓' : '없음 ✗', safe: !!container },
    { desc: '이중 어서션 (위험!)', result: '타입 시스템 우회 — 런타임 오류 가능', safe: false },
  ];

  results.forEach(r => {
    const el = document.createElement('div');
    el.style.marginBottom = '6px'; el.style.fontSize = '11px';
    el.innerHTML = `<span style="color:#f59e0b;">${r.desc}</span><br><span style="color:${r.safe?'#888':'#10b981'}; font-size:10px;">${r.result}</span>`;
    document.currentScript.parentElement.appendChild(el);
  });