ts declare怎么用
时间: 2023-10-01 20:05:02 浏览: 53
在 TypeScript 中,`declare` 关键字用于声明全局变量、函数、类、接口和命名空间等。它通常用于声明那些已经存在于 JavaScript 代码中,但是 TypeScript 编译器无法识别的实体。
下面是一些 `declare` 的用法示例:
1. 声明全局变量:
```typescript
declare var myVar: string;
```
2. 声明全局函数:
```typescript
declare function myFunc(arg: number): void;
```
3. 声明全局类:
```typescript
declare class MyClass {
constructor(name: string);
sayHello(): void;
}
```
4. 声明全局接口:
```typescript
declare interface MyInterface {
name: string;
age: number;
}
```
5. 声明命名空间:
```typescript
declare namespace MyNamespace {
function myFunc(): void;
let myVar: number;
}
```
通过使用 `declare` 关键字,可以让 TypeScript 编译器知道这些实体的存在,避免编译时的错误提示。请注意,`declare` 只是用于编译时的类型检查,并不会在运行时引入任何代码。
相关问题
ts declare使用
In TypeScript, the `declare` keyword is used to tell the compiler that a variable, function, class, or namespace already exists and is defined elsewhere. This is useful when you want to use a library or framework that was written in JavaScript, but you want to write your code in TypeScript.
Here are a few examples of how to use `declare` in TypeScript:
1. Declare a global variable:
```
declare const myVar: string;
```
This tells TypeScript that `myVar` is a global variable of type `string`, but the variable is not defined in the current file.
2. Declare a function:
```
declare function myFunc(param: string): number;
```
This tells TypeScript that `myFunc` is a function that takes a parameter of type `string` and returns a value of type `number`, but the function is not defined in the current file.
3. Declare a class:
```
declare class MyClass {
constructor(param: string);
myMethod(): void;
}
```
This tells TypeScript that `MyClass` is a class with a constructor that takes a parameter of type `string`, and the class has a method called `myMethod` that returns `void`, but the class is not defined in the current file.
4. Declare a namespace:
```
declare namespace MyNamespace {
const myVar: string;
function myFunc(param: string): number;
class MyClass {
constructor(param: string);
myMethod(): void;
}
}
```
This tells TypeScript that `MyNamespace` is a namespace that contains a variable called `myVar`, a function called `myFunc`, and a class called `MyClass`, but the namespace is not defined in the current file.
Using `declare` in TypeScript is a powerful tool for working with existing JavaScript code and libraries.
ts declare
在 TypeScript 中,`declare` 关键字用于告诉编译器某个标识符的类型信息,而不需要实际的实现代码。它可以用于声明全局变量、函数、类、接口等。
例如,你可以使用 `declare` 声明一个全局变量:
```typescript
declare const myVar: number;
```
这样就告诉编译器 `myVar` 是一个全局变量,类型为 `number`,但是并没有提供具体的实现。
`declare` 也可以用于声明全局函数:
```typescript
declare function myGlobalFunction(): void;
```
这样就告诉编译器存在一个名为 `myGlobalFunction` 的全局函数,但是同样没有提供具体的实现。
需要注意的是,`declare` 只用于编译时的类型检查,并不会生成真正的 JavaScript 代码。这意味着在使用 `declare` 声明全局变量或函数时,你需要确保它们在运行时的环境中是可用的。