TypeScript - 命名空间

命名空间是一种逻辑上对相关代码进行分组的方法。这在 TypeScript 中是内置的，不像 JavaScript，在 JavaScript 中变量声明进入全局作用域，如果在同一个项目中使用多个 JavaScript 文件，则可能存在覆盖或误解相同变量的可能性，这将导致 JavaScript 中的“全局命名空间污染问题”。

定义命名空间

命名空间定义以关键字namespace开头，后跟命名空间名称，如下所示：

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

应该在命名空间外部访问的类或接口应该用关键字export标记。

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，则应使用三斜杠引用语法进行引用。

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

以下程序演示了命名空间的使用：

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());
      }
   }
}

可以使用以下命令编译和执行上述代码：

tsc --out app.js TestShape.ts  

node app.js

编译后，它将生成以下 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());

编译并执行上述代码后，将产生以下结果：

Circle is drawn 
Triangle is drawn

嵌套命名空间

您可以按照如下方式在一个命名空间内定义另一个命名空间：

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));

可以使用以下命令编译和执行上述代码：

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

编译后，它将生成以下 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));

编译并执行上述代码后，将产生以下结果：

200