Drex

// 安装
$ npm install -g typescript
$ yarn global add typescript
// 编译 TypeScript 文件
$ tsc helloworld.ts

let isDone: boolean = false;
// ES5：var isDone = false;

let count: number = 10;
// ES5：var count = 10;

let name: string = "Semliker";
// ES5：var name = 'Semlinker';

let list: number[] = [1, 2, 3];
// ES5：var list = [1,2,3];
let list: Array<number> = [1, 2, 3]; // Array<number>泛型语法
// ES5：var list = [1,2,3];

enum Direction {
  NORTH,
  SOUTH,
  EAST,
  WEST,
}
let dir: Direction = Direction.NORTH;

"use strict";
var Direction;
(function(Direction) {
  Direction[(Direction["NORTH"] = 0)] = "NORTH";
  Direction[(Direction["SOUTH"] = 1)] = "SOUTH";
  Direction[(Direction["EAST"] = 2)] = "EAST";
  Direction[(Direction["WEST"] = 3)] = "WEST";
})(Direction || (Direction = {}));
var dir = Direction.NORTH;

enum Direction {
NORTH = 3,
SOUTH,
EAST,
WEST,
}

enum Direction {
NORTH = "NORTH",
SOUTH = "SOUTH",
EAST = "EAST",
WEST = "WEST",
}

"use strict";
var Direction;
(function(Direction) {
  Direction["NORTH"] = "NORTH";
  Direction["SOUTH"] = "SOUTH";
  Direction["EAST"] = "EAST";
  Direction["WEST"] = "WEST";
})(Direction || (Direction = {}));

enum Enum {
A,
B,
C = "C",
D = "D",
E = 8,
F,
}

"use strict";
var Enum;
(function(Enum) {
  Enum[(Enum["A"] = 0)] = "A";
  Enum[(Enum["B"] = 1)] = "B";
  Enum["C"] = "C";
  Enum["D"] = "D";
  Enum[(Enum["E"] = 8)] = "E";
  Enum[(Enum["F"] = 9)] = "F";
})(Enum || (Enum = {}));

console.log(Enum.A); //输出：0
console.log(Enum[0]); // 输出：A

let notSure: any = 666;
notSure = "Semlinker";
notSure = false;

let value: any;
value.foo.bar; // OK
value.trim(); // OK
value(); // OK
new value(); // OK
value[0][1]; // OK

let value: unknown;
value = true; // OK
value = 42; // OK
value = "Hello World"; // OK
value = []; // OK
value = {}; // OK
value = Math.random; // OK
value = null; // OK
value = undefined; // OK
value = new TypeError(); // OK
value = Symbol("type"); // OK

let value: unknown;
let value1: unknown = value; // OK
let value2: any = value; // OK
let value3: boolean = value; // Error
let value4: number = value; // Error
let value5: string = value; // Error
let value6: object = value; // Error
let value7: any[] = value; // Error
let value8: Function = value; // Error

let value: unknown;
value.foo.bar; // Error
value.trim(); // Error
value(); // Error
new value(); // Error
value[0][1]; // Error

let tupleType: [string, boolean];
tupleType = ["Semlinker", true];

console.log(tupleType[0]); // Semlinker
console.log(tupleType[1]); // true

tupleType = [true, "Semlinker"];

[0]: Type 'true' is not assignable to type 'string'.
[1]: Type 'string' is not assignable to type 'boolean'.

tupleType = ["Semlinker"];

Property '1' is missing in type '[string]' but required in type '[string, boolean]'.

// 声明函数返回值为 void
function warnUser(): void {
  console.log("This is my warning message");
}

"use strict";
function warnUser() {
  console.log("This is my warning message");
}

let unusable: void = undefined;

let u: undefined = undefined;
let n: null = null;

// 返回 never 的函数必须存在无法达到的终点
function error(message: string): never {
  throw new Error(message);
}
function infiniteLoop(): never {
  while (true) {}
}

type Foo = string | number;
function controlFlowAnalysisWithNever(foo: Foo) {
  if (typeof foo === "string") {
    // 这里 foo 被收窄为 string 类型
  } else if (typeof foo === "number") {
    // 这里 foo 被收窄为 number 类型
  } else {
    // foo 在这里是 never
    const check: never = foo;
  }
}

type Foo = string | number | boolean;

let someValue: any = "this is a string";
let strLength: number = (<string>someValue).length;

let someValue: any = "this is a string";
let strLength: number = (someValue as string).length;

interface Admin {
  name: string;
  privileges: string[];
}
interface Employee {
  name: string;
  startDate: Date;
}
type UnknownEmployee = Employee | Admin;
function printEmployeeInformation(emp: UnknownEmployee) {
  console.log("Name: " + emp.name);
  if ("privileges" in emp) {
    console.log("Privileges: " + emp.privileges);
  }
  if ("startDate" in emp) {
    console.log("Start Date: " + emp.startDate);
  }
}

function padLeft(value: string, padding: string | number) {
  if (typeof padding === "number") {
    return Array(padding + 1).join(" ") + value;
  }
  if (typeof padding === "string") {
    return padding + value;
  }
  throw new Error(`Expected string or number, got '${padding}'.`);
}

interface Padder {
  getPaddingString(): string;
}
class SpaceRepeatingPadder implements Padder {
  constructor(private numSpaces: number) {}
  getPaddingString() {
    return Array(this.numSpaces + 1).join(" ");
  }
}
class StringPadder implements Padder {
  constructor(private value: string) {}
  getPaddingString() {
    return this.value;
  }
}
let padder: Padder = new SpaceRepeatingPadder(6);
if (padder instanceof SpaceRepeatingPadder) {
  // padder的类型收窄为 'SpaceRepeatingPadder'
}

function isNumber(x: any): x is number {
  return typeof x === "number";
}
function isString(x: any): x is string {
  return typeof x === "string";
}

const sayHello = (name: string | undefined) => {
  /* ... */
};

sayHello("Semlinker");
sayHello(undefined);

enum CarTransmission {
  Automatic = 200,
  Manual = 300
}
interface Motorcycle {
  vType: "motorcycle"; // discriminant
  make: number; // year
}
interface Car {
  vType: "car"; // discriminant
  transmission: CarTransmission
}
interface Truck {
  vType: "truck"; // discriminant
  capacity: number; // in tons
}

type Vehicle = Motorcycle | Car | Truck;

const EVALUATION_FACTOR = Math.PI;
function evaluatePrice(vehicle: Vehicle) {
  return vehicle.capacity * EVALUATION_FACTOR;
}
const myTruck: Truck = { vType: "truck", capacity: 9.5 };
evaluatePrice(myTruck);

Property 'capacity' does not exist on type 'Vehicle'.
Property 'capacity' does not exist on type 'Motorcycle'.

function evaluatePrice(vehicle: Vehicle) {
  switch (vehicle.vType) {
    case "car":
      return vehicle.transmission * EVALUATION_FACTOR;
    case "truck":
      return vehicle.capacity * EVALUATION_FACTOR;
    case "motorcycle":
      return vehicle.make * EVALUATION_FACTOR;
  }
}

type Message = string | string[];
let greet = (message: Message) => {
  // ...
};

interface IPerson {
  id: string;
  age: number;
}
interface IWorker {
  companyId: string;
}
type IStaff = IPerson & IWorker;
const staff: IStaff = {
  id: "E1006",
  age: 33,
  companyId: "EFT",
};
console.dir(staff);

myBooks.forEach(() => console.log('reading'));
myBooks.forEach(title => console.log(title));
myBooks.forEach((title, idx, arr) =>
  console.log(idx + '-' + title);
);
myBooks.forEach((title, idx, arr) => {
  console.log(idx + '-' + title);
});

// 未使用箭头函数
function Book() {
  let self = this;
  self.publishDate = 2016;
  setInterval(function() {
    console.log(self.publishDate);
  }, 1000);
}
// 使用箭头函数
function Book() {
  this.publishDate = 2016;
  setInterval(() => {
    console.log(this.publishDate);
  }, 1000);
}

function createUserId(name: string, id: number): string {
  return name + id;
}

let IdGenerator: (chars: string, nums: number) => string;
function createUserId(name: string, id: number): string {
  return name + id;
}
IdGenerator = createUserId;

// 可选参数
function createUserId(name: string, id: number, age?: number): string {
  return name + id;
}
// 默认参数
function createUserId(
  name: string = "Semlinker",
  id: number,
  age?: number
): string {
  return name + id;
}

function push(array, ...items) {
  items.forEach(function(item) {
    array.push(item);
  });
}
let a = [];
push(a, 1, 2, 3);

function add(a: number, b: number): number;
function add(a: string, b: string): string;
function add(a: string, b: number): string;
function add(a: number, b: string): string;
function add(a: Combinable, b: Combinable) {
  if (typeof a === "string" || typeof b === "string") {
    return a.toString() + b.toString();
  }
  return a + b;
}

class Calculator {
  add(a: number, b: number): number;
  add(a: string, b: string): string;
  add(a: string, b: number): string;
  add(a: number, b: string): string;
  add(a: Combinable, b: Combinable) {
    if (typeof a === "string" || typeof b === "string") {
      return a.toString() + b.toString();
    }
    return a + b;
  }
}
const calculator = new Calculator();
const result = calculator.add("Semlinker", " Kakuqo");

let x: number;
let y: number;
let z: number;
let five_array = [0, 1, 2, 3, 4];
[x, y, z] = five_array;

let two_array = [0, 1];
let five_array = [...two_array, 2, 3, 4];

let colors: string[] = ["red", "green", "blue"];
for (let i of colors) {
  console.log(i);
}

let person = {
  name: "Semlinker",
  gender: "Male",
};
let { name, gender } = person;

let person = {
  name: "Semlinker",
  gender: "Male",
  address: "Xiamen",
};
// 组装对象
let personWithAge = { ...person, age: 33 };
// 获取除了某些项外的其它项
let { name, ...rest } = person;

interface Person {
  name: string;
  age: number;
}
let Semlinker: Person = {
  name: "Semlinker",
  age: 33,
};

interface Person {
readonly name: string;
age?: number;
}

let a: number[] = [1, 2, 3, 4];
let ro: ReadonlyArray<number> = a;
ro[0] = 12; // error!
ro.push(5); // error!
ro.length = 100; // error!
a = ro; // error!

class Greeter {
  // 静态属性
  static cname: string = "Greeter";
  // 成员属性
  greeting: string;
  // 构造函数 - 执行初始化操作
  constructor(message: string) {
    this.greeting = message;
  }
  // 静态方法
  static getClassName() {
    return "Class name is Greeter";
  }
  // 成员方法
  greet() {
    return "Hello, " + this.greeting;
  }
}
let greeter = new Greeter("world");

"use strict";
var Greeter = /** @class */ (function() {
  // 构造函数 - 执行初始化操作
  function Greeter(message) {
    this.greeting = message;
  }
  // 静态方法
  Greeter.getClassName = function() {
    return "Class name is Greeter";
  };
  // 成员方法
  Greeter.prototype.greet = function() {
    return "Hello, " + this.greeting;
  };
  // 静态属性
  Greeter.cname = "Greeter";
  return Greeter;
})();
var greeter = new Greeter("world");

let passcode = "Hello TypeScript";
class Employee {
  private _fullName: string;
  get fullName(): string {
    return this._fullName;
  }
  set fullName(newName: string) {
    if (passcode && passcode == "Hello TypeScript") {
      this._fullName = newName;
    } else {
      console.log("Error: Unauthorized update of employee!");
    }
  }
}
let employee = new Employee();
employee.fullName = "Semlinker";
if (employee.fullName) {
  console.log(employee.fullName);
}

class Animal {
  name: string;
  constructor(theName: string) {
    this.name = theName;
  }
  move(distanceInMeters: number = 0) {
    console.log(`${this.name} moved ${distanceInMeters}m.`);
  }
}
class Snake extends Animal {
  constructor(name: string) {
    super(name);
  }
  move(distanceInMeters = 5) {
    console.log("Slithering...");
    super.move(distanceInMeters);
  }
}
let sam = new Snake("Sammy the Python");
sam.move();

class Person {
  #name: string;
  constructor(name: string) {
    this.#name = name;
  }
  greet() {
    console.log(`Hello, my name is ${this.#name}!`);
  }
}
let semlinker = new Person("Semlinker");
semlinker.#name;
// ~~~~~
// Property '#name' is not accessible outside class 'Person'
// because it has a private identifier.

interface GenericIdentityFn<T> {
  (arg: T): T;
}

class GenericNumber<T> {
  zeroValue: T;
  add: (x: T, y: T) => T;
}
let myGenericNumber = new GenericNumber<number>();
myGenericNumber.zeroValue = 0;
myGenericNumber.add = function (x, y) {
  return x + y;
};

interface Person {
  name: string;
  age: number;
}
const sem: Person = { name: "semlinker", age: 30 };
type Sem = typeof sem; // -> Person
function toArray(x: number): Array<number> {
  return [x];
}
type Func = typeof toArray; // -> (x: number) => number[]

interface Person {
name: string;
age: number;
}
type K1 = keyof Person; // "name" | "age"
type K2 = keyof Person[]; // "length" | "toString" | "pop" | "push" | "concat" | "join"
type K3 = keyof { [x: string]: Person }; // string | number

type Keys = "a" | "b" | "c"
type Obj = {
[p in Keys]: any
} // -> { a: any, b: any, c: any }

type ReturnType<T> = T extends (
  ...args: any[]
) => infer R ? R : any;

interface ILengthwise {
  length: number;
}
function loggingIdentity<T extends ILengthwise>(arg: T): T {
  console.log(arg.length);
  return arg;
}

loggingIdentity(3); // Error, number doesn't have a .length property

loggingIdentity({ length: 10, value: 3 });

/\*\*
- node_modules/typescript/lib/lib.es5.d.ts
- Make all properties in T optional
  \*/
  type Partial<T> = {
  [P in keyof T]?: T[P];
  };

interface Todo {
  title: string;
  description: string;
}
function updateTodo(todo: Todo, fieldsToUpdate: Partial<Todo>) {
  return { ...todo, ...fieldsToUpdate };
}
const todo1 = {
  title: "organize desk",
  description: "clear clutter",
};
const todo2 = updateTodo(todo1, {
  description: "throw out trash",
});

{
title?: string | undefined;
description?: string | undefined;
}

// 该类型已内置在TypeScript中
type Pick<T, K extends keyof T> = {
    [P in K]: T[P]
};
interface User {
    id: number;
    name: string;
    age: number;
    gender: number;
    email: string;
}
type PickUser = Pick<User, "id" | "name" | "gender">;
// 等价于
type PickUser = {
    id: number;
    name: string;
    gender: number;
};
let user: PickUser = {
    id: 1,
    name: 'tom',
    gender: 1
};

// 该类型已内置在TypeScript中
// 这里使用了条件类型(Conditional Type)，和JS中的三目运算符效果一致
type Exclude<T, U> = T extends U ? never : T;
interface User {
    id: number;
    name: string;
    age: number;
    gender: number;
    email: string;
}
type keys = keyof User; // -> "id" | "name" | "age" | "gender" | "email"
type ExcludeUser = Exclude<keys, "age" | "email">;
// 等价于
type ExcludeUser = "id" | "name" | "gender";

declare type ClassDecorator = <TFunction extends Function>(
target: TFunction
) => TFunction | void;

function Greeter(target: Function): void {
  target.prototype.greet = function(): void {
    console.log("Hello Semlinker!");
  };
}
@Greeter
class Greeting {
  constructor() {
    // 内部实现
  }
}
let myGreeting = new Greeting();
myGreeting.greet(); // console output: 'Hello Semlinker!';

function Greeter(greeting: string) {
  return function(target: Function) {
    target.prototype.greet = function(): void {
      console.log(greeting);
    };
  };
}
@Greeter("Hello TS!")
class Greeting {
  constructor() {
    // 内部实现
  }
}
let myGreeting = new Greeting();
myGreeting.greet(); // console output: 'Hello TS!';

declare type PropertyDecorator = (
  target: Object,
  propertyKey: string | symbol
) => void;

function logProperty(target: any, key: string) {
delete target[key];
const backingField = "_" + key;
Object.defineProperty(target, backingField, {
writable: true,
enumerable: true,
configurable: true
});
// property getter
const getter = function (this: any) {
const currVal = this[backingField];
console.log(`Get: ${key} => ${currVal}`);
return currVal;
};
// property setter
const setter = function (this: any, newVal: any) {
console.log(`Set: ${key} => ${newVal}`);
this[backingField] = newVal;
};
// Create new property with getter and setter
Object.defineProperty(target, key, {
get: getter,
set: setter,
enumerable: true,
configurable: true
});
}
class Person {
@logProperty
public name: string;
constructor(name : string) {
this.name = name;
}
}
const p1 = new Person("semlinker");
p1.name = "kakuqo";

Set: (name) => semlinker;
Set: (name) => kakuqo;

declare type MethodDecorator = <T>(
  target: Object,
  propertyKey: string | symbol,
  descriptor: TypePropertyDescript<T>
) => TypedPropertyDescriptor<T> | void;

function LogOutput(tarage: Function, key: string, descriptor: any) {
let originalMethod = descriptor.value;
let newMethod = function(...args: any[]): any {
let result: any = originalMethod.apply(this, args);
if(!this.loggedOutput) {
this.loggedOutput = new Array<any>();
}
this.loggedOutput.push({
method: key,
parameters: args,
output: result,
timestamp: new Date()
});
return result;
};
descriptor.value = newMethod;
}
class Calculator {
@LogOutput
double (num: number): number {
return num \* 2;
}
}
let calc = new Calculator();
calc.double(11);
// console ouput: [{method: "double", output: 22, ...}]
console.log(calc.loggedOutput);

declare type ParameterDecorator = (
  target: Object,
  propertyKey: string | symbol,
  parameterIndex: number
) => void;

function Log(target: Function, key: string, parameterIndex: number) {
  let functionLogged = key || target.prototype.constructor.name;
  console.log(
    `The parameter in position ${parameterIndex} at ${functionLogged} has been decorated`
  );
}
class Greeter {
  greeting: string;
  constructor(@Log phrase: string) {
    this.greeting = phrase;
  }
}
// console output: The parameter in position 0
// at Greeter has been decorated

{
  "compilerOptions": {
    /* 基本选项 */
    "target": "es5",                       // 指定 ECMAScript 目标版本: 'ES3' (default), 'ES5', 'ES6'/'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'
    "module": "commonjs",                  // 指定使用模块: 'commonjs', 'amd', 'system', 'umd' or 'es2015'
    "lib": [],                             // 指定要包含在编译中的库文件
    "allowJs": true,                       // 允许编译 javascript 文件
    "checkJs": true,                       // 报告 javascript 文件中的错误
    "jsx": "preserve",                     // 指定 jsx 代码的生成: 'preserve', 'react-native', or 'react'
    "declaration": true,                   // 生成相应的 '.d.ts' 文件
    "sourceMap": true,                     // 生成相应的 '.map' 文件
    "outFile": "./",                       // 将输出文件合并为一个文件
    "outDir": "./",                        // 指定输出目录
    "rootDir": "./",                       // 用来控制输出目录结构 --outDir.
    "removeComments": true,                // 删除编译后的所有的注释
    "noEmit": true,                        // 不生成输出文件
    "importHelpers": true,                 // 从 tslib 导入辅助工具函数
    "isolatedModules": true,               // 将每个文件做为单独的模块 （与 'ts.transpileModule' 类似）.
    /* 严格的类型检查选项 */
    "strict": true,                        // 启用所有严格类型检查选项
    "noImplicitAny": true,                 // 在表达式和声明上有隐含的 any类型时报错
    "strictNullChecks": true,              // 启用严格的 null 检查
    "noImplicitThis": true,                // 当 this 表达式值为 any 类型的时候，生成一个错误
    "alwaysStrict": true,                  // 以严格模式检查每个模块，并在每个文件里加入 'use strict'
    /* 额外的检查 */
    "noUnusedLocals": true,                // 有未使用的变量时，抛出错误
    "noUnusedParameters": true,            // 有未使用的参数时，抛出错误
    "noImplicitReturns": true,             // 并不是所有函数里的代码都有返回值时，抛出错误
    "noFallthroughCasesInSwitch": true,    // 报告 switch 语句的 fallthrough 错误。（即，不允许 switch 的 case 语句贯穿）
    /* 模块解析选项 */
    "moduleResolution": "node",            // 选择模块解析策略： 'node' (Node.js) or 'classic' (TypeScript pre-1.6)
    "baseUrl": "./",                       // 用于解析非相对模块名称的基目录
    "paths": {},                           // 模块名到基于 baseUrl 的路径映射的列表
    "rootDirs": [],                        // 根文件夹列表，其组合内容表示项目运行时的结构内容
    "typeRoots": [],                       // 包含类型声明的文件列表
    "types": [],                           // 需要包含的类型声明文件名列表
    "allowSyntheticDefaultImports": true,  // 允许从没有设置默认导出的模块中默认导入。
    /* Source Map Options */
    "sourceRoot": "./",                    // 指定调试器应该找到 TypeScript 文件而不是源文件的位置
    "mapRoot": "./",                       // 指定调试器应该找到映射文件而不是生成文件的位置
    "inlineSourceMap": true,               // 生成单个 soucemaps 文件，而不是将 sourcemaps 生成不同的文件
    "inlineSources": true,                 // 将代码与 sourcemaps 生成到一个文件中，要求同时设置了 --inlineSourceMap 或 --sourceMap 属性
    /* 其他选项 */
    "experimentalDecorators": true,        // 启用装饰器
    "emitDecoratorMetadata": true          // 为装饰器提供元数据的支持
  }
}