1. let notStr:any = 4    //any 类型
    2. notStr = 'maybe it is a string'
    3. notStr = true
    5. notStr.getName
    6. notStr.getName()
    8. let numberOrString:number | string = 123    // 联合类型
    9. numberOrString = 'abc'
    10. numberOrString = true //报错了