TypeScript 基础类型

TypeScript 复制代码

//基础类型 string,number,boolean
const teacherName:string = 'chen lee';
const teacherAge:number = 28.0;
const isMale:boolean = true;
//数组
const numberArr:number[]=[1,2,3,4,5];
const stringArr:string[]=['1','2','3','4','5'];
const booleanArr:Array<boolean>=[true,false,true];
//对象类型
const user: {name:string,age:number} = {name:'dell',age:18};
const userOne: {name:string,age?:number} = {name:'dell'};

function union(id:string|number)
{
    if(typeof id ==='string')
    {
        console.log(id.toUpperCase());
    }
    else
    {
        console.log(id);
    }
}
union('asd');
type User = {name: string,age:number};
//type Employee = {name: string,age:number,salary:number};
const userTwo:User = {name:'dell',age:18};
const userThree:User = {name:'dell',age:18};
//any
function showMessage(message:any)
{
    console.log(message);
}
//函数类型
function abc(message:string):number
{
    return 1;
}
const def: (age:number)=>number = (age:number)=>{return 1;}
//接口类型Interface
interface Student
{
    age:number;
    sex?:string;
}
//继承
// interface OldStudent extends Student
// {
//     name: string;
// }
//const student:Student = {age:18,sex:'male'};
//const oldstudent:OldStudent = {age:18,sex:'male',name:'dell'};
interface Student
{
    name: string;
}
const student:Student = {age:18,sex:'male',name:'dell'};

//交叉类型
type Employee = User & {salary:number};
const employee:Employee = {name: 'string',age:13,salary:18};
//断言 Assersion
//const dom: HTMLElement = document.getElementById('#root');
//const dom1: undefined = document.getElementById('#root') as undefined;
//const dom2: undefined = <undefined>document.getElementById('#root');
const testString: string = 123 as any as string;

//字面量类型
const str:'ast'= 'ast';
function getPosition(position:'left'|'right'):string
{
    return position;
}

const truthy: true = true;
//
function request(url: string,method:'GET'|'POST'):string
{
    return 'sending request';
}
const params:{url:string,method:string}={url:'imooc',method:'POST'}
request(params.url,params.method as 'GET');
//null ， undefined
//严格校验会报红
//const testObject:null = undefined;
//const testUndefined:undefined = null;
const testObject:undefined = undefined;
const testUndefined:null = null;
function checkNull(abc:string | null)
{
    if(typeof abc === 'string' )
    {
        console.log(abc.toUpperCase());
    }
    //console.log(abc!.toUpperCase());表示一定非null
}
//void类型
function getNumber():void//无返回值
{

}

tsconfig.json

bash 复制代码

{
    "compilerOptions":{
        "noImplicitAny":true,
        "strictNullChecks": true
    }
}

"noImplicitAny":true,//对类型转换做检查

将 "noImplicitAny": true 配置在 TypeScript 项目中，意味着‌禁止隐式使用 any 类型 ‌。当 TypeScript 编译器无法推断出某个变量、参数或属性的类型时，会‌报编译错误 ‌，而不是默认将其视为 any。

核心作用

‌强制显式类型声明‌：所有未标注类型的标识符必须明确指定类型，否则编译失败。
‌提升代码安全性‌：避免因类型推断失败导致的潜在运行时错误。
‌增强可维护性‌：代码意图更清晰，便于团队协作和长期维护。

"strictNullChecks": true//对null和undefined做检查

核心作用‌

‌禁止隐式空值赋值 ‌：在严格模式下，null 和 undefined ‌不能 ‌赋值给其他类型（如 string、number 等），除非显式声明为联合类型（如 string | null）‌‌。
‌强制空值检查 ‌：访问变量属性前必须先判断其是否为 null 或 undefined，避免运行时错误‌‌。
‌类型推断更精确 ‌：变量赋值为 null 会被推断为 null 类型，赋值为 undefined 会被推断为 undefined 类型，而非 any‌‌。