An interface can be named in an extends or implements clause, but a type alias for an object type literal cannot.
An interface can have multiple merged declarations, but a type alias for an object type literal cannot.
相同点
都可以描述一个对象或者函数
interface
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| interface User {
name: string
age: number
}
interface UserApi {
(name: string, age: number):void
}
var user:User = {name: '1', age: 1}
var func: UserApi = (name: string, age: number) => void {
}
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type
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| type User = {
name: string
age: number
}
type SetUser = (name: string, age: number) => void
var user:User = {name: '1', age: 1}
var serUser: SetUser = (name: string, age: number) => void {}
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都允许拓展（extends）
interface extends interface
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| interface Base {
name: string;
}
interface Child extends Base{
setName(name: string): void
}
var a:Child = {
name: '1',
setName(name: string) {
console.log(name)
}
}
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type extends type
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| type User = {
name: string;
}
type NewType = User & {age: number}
var aa:NewType = {name: '1', age:2}
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interface extends type
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| type Name = {
name: string;
}
interface User extends Name {
age: number
}
var user:User = {name: '1', age:1}
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type extends interface
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| interface Name {
name: string
}
type User = Name & {age: number}
var user:User = {name: '1', age: 1}
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不同点
type 可以而 interface 不行
type 可以声明基本类型别名，联合类型，元组等类型
基本类型
联合类型
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| interface A {
name: string
}
interface B {
age: number
}
type User = A & B
var user:User = {name: '1', age:1}
type Name: string
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元组
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| type arr = [number, string, boolean]
var a:arr = [1,'1',true]
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type 语句中还可以使用 typeof 获取实例的 类型进行赋值
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| type UserType = typeof User
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interface 可以而 type 不行
interface 能够声明合并
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| interface User {
name: string
}
interface User {
age: number
}
var user: User = {name: '1', age: 1}
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一般来说，如果不清楚什么时候用interface/type，能用 interface 实现，就用 interface , 如果不能就用 type
