Typescript 不是最常用的易忘知识点

 let obj = { name: 'asd', age: 21, salary: 400, desc: "asdasd", op: ['asd', 'as', 'qwe'] };

    
  
    
 for (let i in obj) {
    
   console.log(obj[i as keyof typeof obj]);
    
 }
    
  
    
 let key = 'name';
    
 console.log(obj[key as 'name']);
    
 console.log(obj[key as keyof typeof obj]);
    
    
    
    

 // 函数泛型约束

    
 interface limit<Y> {
    
   value: Y[];
    
   length: () => number;
    
   join: (str?: Y) => Y;
    
 }
    
 // 对T约束
    
 function fun<Y, T extends limit<Y>>(params: T): Y {
    
   let res: Y = para