TypeScript 命名空间

命名空间是一种逻辑上组织相关代码的方式。这是 TypeScript 内置的，与 JavaScript 不同，在 JavaScript 中，变量的声明会进入全局作用域中，如果在同一个项目中使用多个 JavaScript 文件，则存在可能会覆盖或误解相同变量的情况，这会导致JavaScript中的“全局命名空间污染问题”。

定义一个命名空间

命名空间定义以关键字 namespace 开始，后跟命名空间的名称，如下所示 –

namespace SomeNameSpaceName { 
   export interface ISomeInterfaceName {      }  
   export class SomeClassName {      }  
}

应该通过关键字 export 标记外部命名空间中应访问的类或接口。

要在另一个命名空间中访问类或接口，语法将是namespaceName.className。

SomeNameSpaceName.SomeClassName;

如果第一个命名空间在单独的TypeScript文件中，则应使用三斜线引用语法引用它。

/// <reference path = "SomeFileName.ts" />

以下程序示例了对命名空间的使用：

FileName :IShape.ts 
---------- 
namespace Drawing { 
   export interface IShape { 
      draw(); 
   }
}  

FileName :Circle.ts 
---------- 
/// <reference path = "IShape.ts" /> 
namespace Drawing { 
   export class Circle implements IShape { 
      public draw() { 
         console.log("Circle is drawn"); 
      }  

      FileName :Triangle.ts 
      ---------- 
      /// <reference path = "IShape.ts" /> 
      namespace Drawing { 
         export class Triangle implements IShape { 
            public draw() { 
               console.log("Triangle is drawn"); 
            } 
         } 

         FileName : TestShape.ts 
         /// <reference path = "IShape.ts" />   
         /// <reference path = "Circle.ts" /> 
         /// <reference path = "Triangle.ts" />  
         function drawAllShapes(shape:Drawing.IShape) { 
            shape.draw(); 
         } 
         drawAllShapes(new Drawing.Circle());
         drawAllShapes(new Drawing.Triangle());
      }
   }
}

上述代码可以使用以下命令进行编译和执行：

tsc --out app.js TestShape.ts  

node app.js

在编译时，将生成以下JavaScript代码（app.js）。

//Generated by typescript 1.8.10
/// <reference path = "IShape.ts" />
var Drawing;
(function (Drawing) {
   var Circle = (function () {
      function Circle() {
      }
      Circle.prototype.draw = function () {
         console.log("Cirlce is drawn");
      };
      return Circle;
   }());

   Drawing.Circle = Circle;
})(Drawing || (Drawing = {}));

/// <reference path = "IShape.ts" />
var Drawing;
(function (Drawing) {
   var Triangle = (function () {
      function Triangle() {
      }
      Triangle.prototype.draw = function () {
         console.log("Triangle is drawn");
      };
      return Triangle;
   }());
   Drawing.Triangle = Triangle;
})(Drawing || (Drawing = {}));

/// <reference path = "IShape.ts" />
/// <reference path = "Circle.ts" />
/// <reference path = "Triangle.ts" />
function drawAllShapes(shape) {
   shape.draw();
}

drawAllShapes(new Drawing.Circle());
drawAllShapes(new Drawing.Triangle());

当上述代码被编译和执行时，会产生以下结果 −

Circle is drawn 
Triangle is drawn

嵌套命名空间

您可以按以下方式在另一个命名空间内定义一个命名空间 –

namespace namespace_name1 { 
   export namespace namespace_name2 {
      export class class_name {    } 
   } 
}

您可以使用点 (.) 运算符来访问嵌套命名空间的成员，如下所示−

FileName : Invoice.ts  
namespace tutorialPoint { 
   export namespace invoiceApp { 
      export class Invoice { 
         public calculateDiscount(price: number) { 
            return price * .40; 
         } 
      } 
   } 
} 
FileName: InvoiceTest.ts 

/// <reference path = "Invoice.ts" />
var invoice = new tutorialPoint.invoiceApp.Invoice(); 
console.log(invoice.calculateDiscount(500));

以上代码可使用以下命令进行编译和执行：

tsc --out app.js InvoiceTest.ts 
node app.js

编译时，将会生成以下的JavaScript代码（app.js）。

//Generated by typescript 1.8.10
var tutorialPoint;
(function (tutorialPoint) {
   var invoiceApp;
   (function (invoiceApp) {
      var Invoice = (function () {
         function Invoice() {
         }
         Invoice.prototype.calculateDiscount = function (price) {
            return price * .40;
         };
         return Invoice;
      }());
      invoiceApp.Invoice = Invoice;
   })(invoiceApp = tutorialPoint.invoiceApp || (tutorialPoint.invoiceApp = {}));

})(tutorialPoint || (tutorialPoint = {}));
/// <reference path = "Invoice.ts" />

var invoice = new tutorialPoint.invoiceApp.Invoice();
console.log(invoice.calculateDiscount(500));

当上述代码被编译和执行时，会产生以下结果−

200