如何导入其顶级元素是未导出的命名空间的Typescript类型定义文件? [英] How do you import a Typescript type definition file whose top level element is a non-exported namespace?
问题描述
我正在尝试使用 @types/googlemaps
类型定义文件.
I'm trying to use the @types/googlemaps
type definition file.
代码看起来像
declare namespace google.maps {
/***** Map *****/
export class Map extends MVCObject {
constructor(mapDiv: Element|null, opts?: MapOptions);
fitBounds(bounds: LatLngBounds|LatLngBoundsLiteral): void;
...
...
overlayMapTypes: MVCArray<MapType>;
}
export interface MapOptions {
backgroundColor?: string;
disableDoubleClickZoom?: boolean;
draggable?: boolean;
...
当我尝试在项目中使用此类型定义时,就像这样
When I try to use this type definition in my project, like so
import * as google from 'googlemaps';
我收到一个编译错误,说
I get a compile error saying
Error:(2, 25) TS2306:File 'C:/Users/CodyB/musicappproj/src/node_modules/@types/googlemaps/index.d.ts' is not a module.
为什么它不将此类型定义文件视为模块? 我使用错了吗?定义文件不正确吗?
Why does it not consider this types definition file to be a module? Am I using it wrong ? Is the definition file wrong?
推荐答案
为什么它不将此类型定义文件视为模块?
Why does it not consider this types definition file to be a module?
编译器不将此类型定义文件视为ECMA6模块,因为该文件缺少顶层导出/导入.相反,该文件将其导出嵌套/隐藏在namespace
内并且不导出名称空间.结果,名称空间成为全局范围的一部分,并且文件不成为模块.
The compiler does not consider this type definition file to be an ECMA6 module because the file lacks a top-level export/import. Instead, the file nests/hides its exports inside a namespace
and does not export the namespace. As a result, the namespace becomes part of the global scope, and the file does not become a module.
仅当文件具有顶级导入或导出时,它才是模块.在下面的代码中,foo.ts
和bar.ts
都是模块,但是baz.ts
不是模块,因为它缺少顶级的import
或export
语句.
A file is a module only if it has a top-level import or export. In the following code, both foo.ts
and bar.ts
are modules, but baz.ts
is not, because it lacks a top-level import
or export
statement.
// foo.ts
console.log('foo');
export {}
// bar.ts
import * as foo from './foo';
console.log('bar');
// baz.ts
console.log('baz');
// index.ts
import * as foo from './foo';
import * as bar from './bar';
import * as baz from './baz'; // File 'c:/dev/temp/baz.ts' is not a module.ts(2306)
我使用错了吗?
Am I using it wrong?
是的.您正在像对待文件一样对待文件-事实并非如此.另一种方法是通过其定义的全局名称空间访问其成员.这是两种方法:
Yes. You are treating the file like it is a module - which it is not. The alternative is to access its members through the global namespace it defines. Here are two approaches:
一种方法是像这样点进"命名空间:
One is to 'dot into' the namespace like this:
const div1 = new HTMLDivElement();
const map1 = new google.maps.Map(div1);
另一种方法是使用这种破坏:
Another is to use destructuring like this:
const { Map } = google.maps;
const div2 = new HTMLDivElement();
const map2 = new Map(div2);
定义文件是否错误?
Is the definition file wrong?
不.尽管可以说对于浏览器(例如Firefox)应用程序而言,它比对NodeJS应用程序而言更为传统,但它正在采取一种有效的方法.
No. It is taking a valid approach albeit one that is arguably more conventional for a browser (e.g. Firefox) application than it is for a NodeJS application.
https://www.typescriptlang.org/docs/handbook/namespaces.html
https://www.typescriptlang.org/docs/handbook /namespaces-and-modules.html
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