共同点

• 都能描述函数、对象的类型信息

• 允许彼此/互相继承

  • type & type

       type IPerson = {
           name: string;
       }
       type IStudent = IPerson & {
           age: number;
       }
       // type：不允许重复定义，所以不会进行合并
       let obj: IStudent = {
           name: 'lily',
           age: 19
       }
    

  • type & interface

        interface IPerson {
            name: string;
          }
        type IStudent = IPerson & {
            age: number;
         }
       // type：不允许重复定义，所以不会进行合并
       let obj: IStudent = {
           name: 'lily',
           age: 19
        }
    

  • interface & interface

        interface IPerson {
            name: string;
        }
        interface IStudent extends IPerson {
            age: number;
        }
        // type：不允许重复定义，所以不会进行合并
        let obj: IStudent = {
            name: 'lily',
            age: 19
        }
    

  • interface & interface

        interface IPerson {
        name: string;
        }
        interface IStudent extends IPerson {
            age: number;
        }
        // type：不允许重复定义，所以不会进行合并
        let obj: IStudent = {
            name: 'lily',
            age: 19
        }
    

• type、interface 交集和并集

  type

  type IPerson = {
     name: string;
     age: number;
  
  }
  type IStudent = {
     age: number;
     count: number;
  }
  // 交集
  let obj: IStudent | IPerson = {
     name: 'lily',
     age: 19
  }
  // 并集
  let obj2: IStudent & IPerson = {
     name: 'lily',
     age: 19,
     count: 10
  
  }
  

  interface

  interface IPerson {
  name: string;
  age: number;
  }
  interface IStudent {
     age: number;
     count: number;
  }
  // 交集
  let obj: IStudent | IPerson = {
     name: 'lily',
     age: 19
  }
  // 并集
  let obj2: IStudent & IPerson = {
     name: 'lily',
     age: 19,
     count: 10
  
  }
  

不同点

• interface重复定义会合并,type不会

      interface IPerson {
          name: string;
      }
      interface IPerson {
          age: number;
      }
      // IPerson被合并了
      let obj: IPerson = {
          name: 'lily',
          age: 19
      }
  

• type不允许重复定义，直接报错，所以没有合并

• type可以定义 类型别名与字符串字面量类型，interface不可以

  type TName = string; // 类型别名
  type IPerson = {
      name: TName;
  }
  
  let student: IPerson = {
      name: 'lily'
  };
  // 字符串字面量类型
  type TCode = '1' | '2' | '5'; 
  const str: TCode = '1';// 合法
  const str2: TCode = '9'; // 非法