• 可多不可少

正确示例：

interface TestInterface {
    name: string;
}

let p1 = {name: 'BNTang'};
let p2 = {age: 18};
let p3 = {name: 'BNTang', age: 18};

let t: TestInterface;
t = p1;
t = p3;

错误示例：

interface TestInterface {
    name: string;
}

let p1 = {name: 'BNTang'};
let p2 = {age: 18};
let p3 = {name: 'BNTang', age: 18};

let t: TestInterface;
t = p1;
t = p2;
t = p3;

• 会递归检查

改造如上接口约束代码，添加子属性如下：

interface TestInterface {
    name: string;
    children: {
        age: number
    };
}

然后再次进行测试，正确示例：

interface TestInterface {
    name: string;
    children: {
        age: number
    };
}

let p1 = {name: 'BNTang', children: {age: 18}};
let p2 = {name: 'BNTang', children: {age: 'abc'}};

let t: TestInterface;
t = p1;

错误示例，因为 p2 当中的 age 属性是字符串类型：

interface TestInterface {
    name: string;
    children: {
        age: number
    };
}

let p1 = {name: 'BNTang', children: {age: 18}};
let p2 = {name: 'BNTang', children: {age: 'abc'}};

let t: TestInterface;
t = p1;
t = p2;