接口是实体应遵循的语法合约.换句话说，接口定义了任何实体必须遵守的语法.
接口定义属性，方法和事件，它们是接口的成员.接口仅包含成员的声明.派生类负责定义成员.它通常有助于提供派生类所遵循的标准结构.
让我们考虑一个对象 :
var person = {
FirstName:"Tom",
LastName:"Hanks",
sayHi: ()=>{ return "Hi"}
};如果我们考虑对象的签名，它可能是 :
{
FirstName:string,
LastName:string,
sayHi()=>string
}要在对象之间重用签名，我们可以将其定义为接口.
interface关键字用于声明接口.以下是声明接口的语法 :
interface interface_name {
}interface IPerson {
firstName:string,
lastName:string,
sayHi: ()=>string
}
var customer:IPerson = {
firstName:"Tom",
lastName:"Hanks",
sayHi: ():string =>{return "Hi there"}
}
console.log("Customer Object ")
console.log(customer.firstName)
console.log(customer.lastName)
console.log(customer.sayHi())
var employee:IPerson = {
firstName:"Jim",
lastName:"Blakes",
sayHi: ():string =>{return "Hello!!!"}
}
console.log("Employee Object ")
console.log(employee.firstName);
console.log(employee.lastName);该示例定义了一个接口.客户对象的类型为IPerson.因此，它现在将绑定在对象上以定义接口指定的所有属性.
具有以下签名的另一个对象仍被视为IPerson，因为该对象由其大小处理或者签名.
在编译时，它将生成以下JavaScript代码.
//Generated by typescript 1.8.10
var customer = { firstName: "Tom", lastName: "Hanks",
sayHi: function () { return "Hi there"; }
};
console.log("Customer Object ");
console.log(customer.firstName);
console.log(customer.lastName);
console.log(customer.sayHi());
var employee = { firstName: "Jim", lastName: "Blakes",
sayHi: function () { return "Hello!!!"; } };
console.log("Employee Object ");
console.log(employee.firstName);
console.log(employee.lastName);上面示例代码的输出如下 :
Customer object Tom Hanks Hi there Employee object Jim Blakes Hello!!!
接口不能转换为JavaScript.它只是TypeScript的一部分.如果您看到TS Playground工具的屏幕截图，则在声明与类不同的接口时，不会发出任何java脚本.因此，接口对运行时JavaScript的影响为零.
以下示例显示了使用Union Type和Interface :
interface RunOptions {
program:string;
commandline:string[]|string|(()=>string);
}
//commandline as string
var options:RunOptions = {program:"test1",commandline:"Hello"};
console.log(options.commandline)
//commandline as a string array
options = {program:"test1",commandline:["Hello","World"]};
console.log(options.commandline[0]);
console.log(options.commandline[1]);
//commandline as a function expression
options = {program:"test1",commandline:()=>{return "**Hello World**";}};
var fn:any = options.commandline;
console.log(fn());在编译时，它将生成以下JavaScript代码.
//Generated by typescript 1.8.10
//commandline as string
var options = { program: "test1", commandline: "Hello" };
console.log(options.commandline);
//commandline as a string array
options = { program: "test1", commandline: ["Hello", "World"] };
console.log(options.commandline[0]);
console.log(options.commandline[1]);
//commandline as a function expression
options = { program: "test1", commandline: function () { return "**Hello World**"; } };
var fn = options.commandline;
console.log(fn());其输出如下 :
Hello Hello World ** Hello World **
接口可以定义数组使用的键类型以及它包含的条目类型.索引可以是字符串或类型编号.
interface namelist {
[index:number]:string
}
var list2:namelist = ["John",1,"Bran"] //Error. 1 is not type string
interface ages {
[index:string]:number
}
var agelist:ages;
agelist["John"] = 15 // Ok
agelist[2] = "nine" // Error接口可以被其他接口扩展.换句话说，接口可以从其他接口继承. Typescript允许接口从多个接口继承.
使用extends关键字实现接口之间的继承.
Child_interface_name extends super_interface_name
Child_interface_name extends super_interface1_name, super_interface2_name,…,super_interfaceN_name
interface Person {
age:number
}
interface Musician extends Person {
instrument:string
}
var drummer = <Musician>{};
drummer.age = 27
drummer.instrument = "Drums"
console.log("Age: "+drummer.age) console.log("Instrument: "+drummer.instrument)在编译时，它将生成以下JavaScript代码.
//Generated by typescript 1.8.10
var drummer = {};
drummer.age = 27;
drummer.instrument = "Drums";
console.log("Age: " + drummer.age);
console.log("Instrument: " + drummer.instrument);其输出如下 :
Age: 27 Instrument: Drums
interface IParent1 {
v1:number
}
interface IParent2 {
v2:number
}
interface Child extends IParent1, IParent2 { }
var Iobj:Child = { v1:12, v2:23}
console.log("value 1: "+this.v1+" value 2: "+this.v2)对象Iobj属于接口叶子类型.借助继承的接口叶子现在分别具有两个属性-v1和v2.因此，对象Iobj现在必须包含这些属性.
在编译时，它将生成以下JavaScript代码.
//由typescript生成1.8.10
var Iobj = {v1:12，v2:23};
console.log("value 1:"+ this.v1 +"value 2:"+ this.v2);上述代码的输出如下 :
value 1: 12 value 2: 23
