1. // 布尔类型
  2. let isDone: boolean = false;
  3. // number类型
  4. let age: number = 10;
  5. // string类型
  6. let firstName: string = "Felix";
  7. let fullName: string = `${firstName} Chan`;
  8. // undefined类型
  9. let u: undefined = undefined;
  10. // null类型
  11. let n: null = null;
  13. isDone = undefined;
  14. age = undefined;
  15. firstName = undefined;
  16. fullName = undefined;
  17. u = undefined;
  18. n = undefined;
  20. console.log(isDone);
  21. console.log(age);
  22. console.log(firstName);
  23. console.log(fullName);
  24. console.log(u);
  25. console.log(n);
  27. isDone = null;
  28. age = null;
  29. firstName = null;
  30. fullName = null;
  31. u = null;
  32. n = null;
  34. console.log(isDone);
  35. console.log(age);
  36. console.log(firstName);
  37. console.log(fullName);
  38. console.log(u);
  39. console.log(n);
  41. // 任意类型, 不做任何校验
  42. let noSure: any = 4;
  43. noSure = true;
  44. noSure.myName;
  45. noSure.getName();

undefined和null是任意数据类型的子类, 任意类型都可以赋值为undefined和null