HarmonyOS系统开发ArkTS基础编程语法

2024-04-19 11:13:24

一、变量及类型

二、函数

三、类

四、枚举

五、模块化

ArkTS基础编程语法的在线练习地址：https://www.typescriptlang.org/zh/play?#code/Q

一、变量及类型

1、变量声明
let 声明变量，赋值后可以修改
const 声明常量，赋值后便不能再修改
案例：

  let   a:number=100;
  const b:number=200;

2、类型推断
let a=100;
const b=200;
根据初始值进类型推断
console.log(typeof c); //number 类型

3、数据类型
number 表示数字，包括整数和浮点数
string 表示字符串，单双引号均可。
boolean 表示布尔值： true 、 false
数组类型：元素类型[]
对象（object）类型：属性名称和属性值组成的数据结构

let a :number = 100
let b :number = -33
let c :number = 2.5
let d :number = -3.9

let a:string = '你好'
let b:string = "hello"

let isOpen:boolean = true
let isDone:boolean = false

let a: number[] = []
let b: string[] = ['你好', 'hello']

let person: {name:string, age:number, gender:string} = {name:'张三', age:10, gender:'男'};
let person={name:'张三', age:10, gender:'男'};

二、函数

1、函数
function 函数名(参数列表)：返回值类型 {方法体}
function sum(a:number,b:number): number{
return a+b
}

注意：返回值类型不写，会自动推断
function sum(a: number, b: number) {
return a + b;
}

1.1特殊语法
=====================================================
可选参数：参数+? 占位,传值显示，不传值则显示 undefined
function getPersonInfo(name: string, age?: number): string {
return `name:${name},age:${age}`;
}

let p1 = getPersonInfo('zhagnsan')
console.log(p1); // "name:zhagnsan,age:undefined"
=====================================================
默认参数：不传值，则使用默认参数
function getPersonInfo(name: string, age: number=20): string {
return `name:${name},age:${age}`;
}

let p1 = getPersonInfo('zhagnsan')
console.log(p1); // "name:zhagnsan,age:20"

1.2特殊类型
=====================================================
联合类型：一个函数可能处理不同类型的值，这种函数就是联合类型
function printNumberOrString(message: number | string) {
console.log(message)
}
printNumberOrString('a')
printNumberOrString(1)
=====================================================
任意类型：函数需要处理任意类型的值，使用 any 类型
function print(message:any) {
console.log(message)
}
print('a')
print(1)
print(true)

2、匿名函数与箭头函数
forEach()接收函数作为参数，每遍历一次数据调用一次函数。
2.1匿名函数
变化过程
=====================================================
定义函数，将函数名作为 forEach() 参数
let numbers: number[] = [1, 2, 3, 4, 5]
function print(num:number):void{
console.log(num);
}
numbers.forEach(print)
=====================================================
直接将函数的定义写在 forEach() 中
let numbers: number[] = [1, 2, 3, 4, 5]
numbers.forEach(function print(num:number):void{
console.log(num);
})
=====================================================
函数名可以省略
参数类型可以省略（根据上下文自动判断）
返回值类型可以省略（根据上下文自动判断）
适用于简单且仅需1次性使用的场景
let numbers: number[] = [1, 2, 3, 4, 5]
numbers.forEach(function (num){
console.log(num);
})


2.2箭头函数
即lambda表达式，即对匿名函数进一步简化
=====================================================
function可以省略，参数列表和函数体用箭头代替
let numbers: number[] = [1, 2, 3, 4, 5]
numbers.forEach((num)=>{
console.log(num);
})
=====================================================
参数只有一个，括号（）可以省略
let numbers: number[] = [1, 2, 3, 4, 5]
numbers.forEach( num =>{
console.log(num);
})
=====================================================
函数体只有一行代码，花括号{}可以省略，分号';'可以去掉
let numbers: number[] = [1, 2, 3, 4, 5]
numbers.forEach( num =>
console.log(num)
)

三、类

1、类的定义
class Person {
id:number;
name: string;
age: number = 18;
constructor(id: number, name: string,age: number) {
this.id = id;
this.name = name;
this.age = age;
}
introduce(): string {
return `hello,I am ${this.name},and I am ${this.age} years old`
}
}

2、创建对象
let person = new Person(1,'夏天',32)

3、属性和方法调用
console.log(person.age)
console.log(person.introduce())

4、静态成员（静态属性与静态方法）
class Utils{
static count:number=1;
static toLowerCase(str:string){
return str.toLowerCase();
}
}
console.log(Utils.count);
console.log(Utils.toLowerCase('Hello World'));

5、继承
class Person {
id:number;
name: string;
age: number = 18;
constructor(id: number, name: string,age: number) {
this.id = id;
this.name = name;
this.age = age;
}
introduce(): string {
return `hello,I am ${this.name},and I am ${this.age} years old`
}
}

class Student extends Person {
classNumber: string;
constructor(id: number, name: string,age: number, classNumber: string) {
super(id, name,age);
this.classNumber = classNumber;
}
introduce(): string {
return super.introduce()+`, and I am a student`;
}
}
let student = new Student(1,'xiaoming',21,'三年⼆班');
console.log(student.introduce());


6、访问修饰符
class Person {
private id:number;
private name: string;
private age: number = 18;
constructor(id: number, name: string,age: number) {
this.id = id;
this.name = name;
this.age = age;
}
introduce(): string {
return `hello,I am ${this.name},and I am ${this.age} years old`
}

getId() {
return this.id;
}

setId(id:number) {
this.id = id;
}

getName() {
return this.name;
}

setName(name:string) {
this.name = name;
}

getAge() {
return this.age;
}

setAge(age:number) {
this.age = age;
}
}

let person = new Person(1,'夏天',32)

console.log(person.getId())
console.log(person.getName())
console.log(person.getAge())

7、接口（interface）
interface Person {
id: number;
name: string;
introduce(): void;
}

class Student implements Person {
id: number;
name: string;
age: number;
constructor(id: number, name: string, age: number) {
this.id = id;
this.name = name;
this.age = age;
}
introduce(): void {
console.log('Hello,I am a student');
}
}

let s1: Student = new Student(1, 'zhangsan', 17);
console.log(s1.id);
console.log(s1.name);
console.log(s1.age);
s1.introduce();

8、多态
class Teacher implements Person {
id:number;
name:string;
age:number;
constructor(id:number, name:string, age:number) {
this.id = id;
this.name = name;
this.age = age;
}
introduce(): void {
console.log('Hello,I am a teacher');
}
}

let p1: Person = new Student(1, 'zhangsan', 17);
let p2: Person = new Teacher(2, 'lisi', 35);
p1.introduce();//Hello,I am a student
p2.introduce();//Hello,I am a teacher

8、使用接口描述对象类型
interface Person {
name: string;
age: number;
gender: string;
}
let person: Person = {name:'张三', age:10, gender:'男'};

四、枚举

enum Direction {
UP = 'up',
BOTTOM = 'bottom',
LEFT = 'left',
RIGHT = 'right'
}
console.log(Direction.UP) //up
console.log(Direction.BOTTOM) //bottom

五、模块化

export导出，imiport导入
   =======================================================
   使用花括号导出多个，产生问题，容易命名冲突
moduleA.ts
export function sayHello() {
console.log('hello module A');
}
export const printStr = 'hello world';

moduleB.ts
export function sayHello() {
console.log('hello module A');
}
export const printStr = 'hello world';

moduleC.ts
import { sayHello, printStr } from './moduleA';
import { sayHello, printStr } from './moduleB';

   =======================================================
   导入模块重命名，产生问题：冲突内容较多时，写法会冗长
moduleA.ts
export function sayHello() {
console.log('hello module A');
}
export const printStr = 'hello world';

moduleB.ts
export function sayHello() {
console.log('hello module A');
}
export const printStr = 'hello world';

moduleC.ts
import { sayHello as shA, printStr as psA } from './moduleA';
import { sayHello as shB, printStr as psB } from './moduleB';

   =======================================================
   直接模块对象命名，对象调用（推荐）
moduleA.ts
export function sayHello() {
console.log('hello module A');
}
export const printStr = 'hello world';

moduleB.ts
export function sayHello() {
console.log('hello module A');
}
export const printStr = 'hello world';

moduleC.ts
import * as A from './moduleA';
import * as B from './moduleB';
   A.sayHello();
   B.sayHello();

=======================================================
默认导出（加default），默认导入
moduleA.ts
export default function sayHello() {
console.log('hello module A');
}

moduleC.ts
import sayHelloA from './moduleA';
sayHelloA();

码农公寓

一、变量及类型

二、函数

三、类

四、枚举

五、模块化

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