命名空间介绍

命名空间一个最明确的目的就是解决重名问题。
假设这样一种情况，当一个班上有两个名叫小明的学生时，为了明确区分它们，我们在使用名字之外，不得不使用一些额外的信息，比如他们的姓（王小明，李小明），或者他们父母的名字等等。
命名空间定义了标识符的可见范围，一个标识符可在多个名字空间中定义，它在不同名字空间中的含义是互不相干的。这样，在一个新的名字空间中可定义任何标识符，它们不会与任何已有的标识符发生冲突，因为已有的定义都处于其他名字空间中。
TypeScript 中命名空间使用 namespace 来定义，语法格式如下：

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

要在另外一个命名空间调用语法格式为：

SomeNameSpaceName.SomeClassName;

如果一个命名空间在一个单独的 TypeScript 文件中，则应使用三斜杠 /// 引用它，语法格式如下：

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

演示

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

用 tsc 命令编译以上代码：
tsc —out app.js TestShape.ts

得到以下 JavaScript 代码：

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

使用 node 命令查看输出结果为：
$ node app.js
Circle is drawn
Triangle is drawn

嵌套命名空间(总有一些不明觉历的语法)

命名空间支持嵌套，即你可以将命名空间定义在另外一个命名空间里头。

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

成员的访问使用点号 . 来实现，如下实例：

// Invoice.ts
namespace Runoob { 
   export namespace invoiceApp { 
      export class Invoice { 
         public calculateDiscount(price: number) { 
            return price * .40; 
         } 
      } 
   } 
}
// InvoiceTest.ts
/// <reference path = "Invoice.ts" />
var invoice = new Runoob.invoiceApp.Invoice(); 
console.log(invoice.calculateDiscount(500));

tsc —out app.js InvoiceTest.ts

var Runoob;
(function (Runoob) {
    var invoiceApp;
    (function (invoiceApp) {
        var Invoice = /** @class */ (function () {
            function Invoice() {
            }
            Invoice.prototype.calculateDiscount = function (price) {
                return price * .40;
            };
            return Invoice;
        }());
        invoiceApp.Invoice = Invoice;
    })(invoiceApp = Runoob.invoiceApp || (Runoob.invoiceApp = {}));
})(Runoob || (Runoob = {}));
/// <reference path = "Invoice.ts" />
var invoice = new Runoob.invoiceApp.Invoice();
console.log(invoice.calculateDiscount(500));

使用 node 命令查看输出结果为：
$ node app.js
200

李俊扬的技术分享

TypeScript的命名空间

推荐使用 Module

命名空间介绍

演示

嵌套命名空间(总有一些不明觉历的语法)