如何使用reduce替换打字稿中的过滤器和映射

Question

我有一个简单的例子，比如

    interface employer {
      name: string;
      age: number;
    }

    const arr: employer[] = [{name:'Amy',age:18},{name:'Bob',age:20}];

    let data = arr.reduce((c, b) =>  b.age > 18 ? [...c, b] : c,[])

    console.log(data)

我只想归档 arr 数组并返回此人的年龄高于 18 岁，例如 但我得到错误

No overload matches this call.
  Overload 1 of 3, '(callbackfn: (previousValue: employer, currentValue: employer, currentIndex: number, array: employer[]) => employer, initialValue: employer): employer', gave the following error.
    Type 'employer[]' is missing the following properties from type 'employer': name, age
  Overload 2 of 3, '(callbackfn: (previousValue: never[], currentValue: employer, currentIndex: number, array: employer[]) => never[], initialValue: never[]): never[]', gave the following error.
    Type 'employer[]' is not assignable to type 'never[]'.
      Type 'employer' is not assignable to type 'never'.

为此b.age > 18 ? [...c, b] : c 我认为它适用于javascript 我们该如何解决？ 谢谢

Answer 1

为了修复此错误，您需要在reduce 函数上添加类型。你可以通过调用来做到这一点

let data = arr.reduce<employer[]>((c, b) =>  b.age > 18 ? [...c, b] : c,[])

另外，这是有效的

let data = arr.reduce((c, b) =>  b.age > 18 ? [...c, b] : c,[] as employer[])

但我认为第一个看起来更好。

您可以在 playground 中找到一个工作示例

Answer 2

我尝试另一种方式

interface employer { 
      name: string; 
      age: number; 
    } 
 
    const arr: employer[] = [{name:'Amy',age:18},{name:'Bob',age:20}]; 
 
    let data = arr.reduce((c:any, b:any) =>  b.age > 18 ? [...c, b] : c,[]) 
 
    console.log(arr)