interfaceAdmin{name:string;privileges:string[];}interfaceEmployee{name:string;startDate:Date;}type UnknownEmployee=Employee|Admin;functionprintEmployeeInformation(emp:UnknownEmployee){console.log("Name: "+emp.n
Using these enum types in real-world cases is quite straightforward because we can simply declare them as types and pass them as arguments to functions. Because number-based enums automatically increment their values, there’s a potential issue when enum members don’t have explicit initial values...
interface Person { name: string; age: number; } type x = Person["name"]; // x is string 内置工具类型 Required 将类型的属性变成必选,当缺少属性时,就会报错。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 interface Person { name?: string, age?: number, hobby?: string[] } const ...
If we were to debug a program, it is easier to read string values rather than numeric values. Consider the same example of a numeric enum, but represented as a string enum: Example: String Enum Copy enum PrintMedia { Newspaper = "NEWSPAPER", Newsletter = "NEWSLETTER", Magazine = "...
enum Direction { NORTH = 3, SOUTH, EAST, WEST, }2.字符串枚举在TypeScript 2.4 版本,允许我们使用字符串枚举。在一个字符串枚举里,每个成员都必须用字符串字面量,或另外一个字符串枚举成员进行初始化。enum Direction { NORTH = "NORTH", SOUTH = "SOUTH", EAST = "EAST", WEST = "WEST", }以上...
let someValue: any = "this is a string"; let strLength: number = (someValue as string).length; 四、类型守卫 A type guard is some expression that performs a runtime check that guarantees the type in some scope. —— TypeScript 官方文档 类型保护是可执行运行时检查的一种表达式,用于确保该...
Object data type has a broader scope and allows to store pretty much anything. Thus, even if we have non-strings in a place that is supposed to be a string, we don’t get any error. It is always better to have a dedicated data type. For instance, if we try to the example above...
enum 支持反向映射,也就是说,可以通过值来获得成员、成员名。 回顾之前 CardSuit 的例子: const clubsAsNumber: number = CardSuit.Clubs; // 3 const clubsAsString: string = CardSuit[0]; // 'Clubs' 函数 你可以为每个参数指定一个类型,再为函数指定一个返回类型。 function add(x: number, y: numb...
TypeScript 最常见的三种类型 string、number、boolean、null 、 undefined let str: string = 'hello world' // 字符串 let count: number = 100 // 数字 let id:string = 1 // 字符串或数字 let flag: boolean = true // 布尔 let a: null = null // null ...
TypeScript enum 反向映射 / 双向映射 All In One TypeScript enum 枚举实现原理 JS enum enumDirection{Up,Down,Left,Right}// jsvarDirection; (function(Direction) {Direction[Direction["Up"] =0] ="Up";Direction[Direction["Down"] =1] ="Down";Direction[Direction["Left"] =2] ="Left";Direction...