10.类型推断

一.赋值推断

赋值时推断，类型从右像左流动,会根据赋值推断出变量类型

let str = 'zhufeng';
let age = 11;
let boolean = true;

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自动推断函数返回值类型

function sum(a: string, b: string) {
    return a + b;
}
sum('a','b');

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函数从左到右进行推断

type Sum = (a: string, b: string) => string;
const sum: Sum = (a, b) => a + b;

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可以通过属性值,推断出属性的类型

let person = {
    name:'zf',
    age:11
}
let {name,age} = person;

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可以使用typeof关键字反推变量类型

let person = {
    name:'zf',
    age:11
}
type Person = typeof person

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interface IPerson {
    name:string,
    age:number,
    job:{
        address:string
    }
}
type job = IPerson['job']

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interface IPerson {
    name:string,
    age:number
}
type MapPerson = {[key in keyof IPerson]:IPerson[key]}

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