?變量定義方式

# 變量聲明
let msg: string = 'douzi'
console.log(msg)
let num: number = 20
console.log(num)
let end: boolean = true
console.log("end=" + end)
let a: any = 10
a = 'douzi'
console.log(a)
let p = {name:"douzi",age:20}
console.log(p.name)
console.log("age=" + p['age'])
let names: Array<string> = ["douzi","douzi1"]
console.log(names[0])
let ages: number[] = [20,21]
console.log("age1=" + ages[1])

?條件定義方式

# 條件語法
if(num % 2 == 0) {
    console.log("num 是偶數(shù)")
}else {
    console.log("num 是奇數(shù)")
}

if (num > 0) {
    console.log("num 是正數(shù)")
}else if(num < 0){
    console.log("num 是負(fù)數(shù)")
} else {
    console.log("num 是0")
}

# switch 
switch(msg) {
    case 'douzi': {
        console.log("douzi")
        break
    }
    case 'douzi1': {
        console.log("douzi1")
        break
    }
    default: {
        console.log('douzi2')
        break
    }
}

?循環(huán)定義方式

# 循環(huán)語法
for(let i = 0; i < 10; i++) {
    console.log("for i=" + i)
}

let i = 0;
while(i < 10) {
    console.log('while i=' + i ++)
}

let names: Array<string> = ["douzi","yuehua"]
// for in 迭代器，獲取數(shù)組角標(biāo)  const = let
for (const i in names) {
    console.log(i + "=" + names[i])
}
// for of 迭代器，獲取數(shù)組元素
for (const name of names) {
    console.log("of name = " + name)
}

?函數(shù)定義方式

# 無返回值函數(shù)  :void 可以省略
function helloWorld(name:String, age:number): void {
    console.log("name=" + name + ",age=" + age + ",Hello World!")
}

# 無返回值函數(shù)簡寫方式
let helloWorld = (name:String, age:number) => {
    console.log("name=" + name + ",age=" + age + ",Hello World!")
}

helloWorld('douzi', 40)

# 有返回值函數(shù)
function sum(x: number, y: number): number {
    return x + y
}

# 有返回值函數(shù)簡寫方式
let sum = (x: number, y: number): number => {
    return x + y
}
let result = sum(10, 20)
console.log("10 + 20 = " + result)


# 可選參數(shù)，？代表參數(shù) 可傳 可不傳
let sayHello = (name ?:String) => {
    name = name ? name : 'yuehua'
    console.log("Hello " + name)
}
sayHello()
sayHello('douzi')


# 入?yún)⒛J(rèn)值 當(dāng)不傳參數(shù)時(shí)，使用默認(rèn)值
let sayHello = (name :String = 'yuehua') => {
    console.log("Hello " + name)
}
sayHello()
sayHello('douzi')

類和接口的定義

# 接口繼承
enum Msg {
    HI = 'Hi',
    HELLO = 'Hello'
}

interface A {
    say(msg: Msg): void
}

class B implements A {
  say(msg: Msg) {
    console.log(msg + ", I am B")
  }
}

let a:A = new B()
a.say(Msg.HELLO)

# 類繼承
class Rectangle {
    private width: number
    private height: number
    constructor(width: number,height: number) {
        this.height = height;
        this.width = width
    }    
    public area(): number {
        return this.width * this.height
    }
}
class Square extends Rectangle {
    constructor(side: number) {
        super(side, side)
    }
}

let s:Square = new Square(5)
console.log('正方形邊為5的area=' + s.area())

ets文件中的重要 關(guān)鍵字

struct Index?? 自定義組件：可復(fù)用的UI單元

@Component??? 自定義組件

@Entry????????????? 當(dāng)前組件是入口組件

@State????????????? 標(biāo)記變量為狀態(tài)變量，值變化會(huì)觸發(fā)UI刷新

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