/*  断言
确定后期一定是某种格式
可用于表单大对象初始化是空，赋值时有具体字段。前期断言是会是某种格式
*/interface obj {name: stringlocation: stringage?: number
}// 会报错
// let data: obj = {
// 
// } 
let data: obj = {} as obj; // 断言data会有obj里的字段
data.name = "全易";
data.location = "北京";
data.age = 18interface fnT {(n: number): stringtitle: stringage?: number
}
let fn: fnT = function (n: number) {return "123"
} as fnT; // 断言后面会添加title
fn.title = "哈哈哈"