ts学习6-类型断言 联合类型 交叉类型

类型断言 联合类型 交叉类型

联合类型

let phone: number|string = 114514
phone = '114-514'

交叉类型

interface Student {
	name:string
    age:number,
    score:number,
    exam():number
}

interface Child {
    happy:boolean
}

const analyseChildStudent = (cs:Child & Student):void => {
    console.log(cs.age)
    console.log(cs.score)
    console.log(cs.happy)
}

analyseChildStudent({
    name:'张三',
    age:11,
    score:59,
    exam(): number {
        return this.score++;
    },
    happy:false,
})

类型断言（慎用）

只能欺骗编译器通过编译，并不能让类型真的发生变化

const phoneLength = (phone:number | string):number => {
    return (phone as string).length
}
const phoneLength = (phone:number | string):number => {
    return (<string>phone).length
}