typescript - 如何从 TypeScript 中的类型化对象中动态删除键

Question

如何从类型对象中动态删除键？

例如，我的接口(interface)QUERY_PARAMS是:

export interface QUERY_PARAMS {
  query: string;
  min_height?: string;
  max_height?: string;
  min_width?: string;
  max_width?: string;
  color?: string;
  image_type?: IMAGETYPE;
  order?: ORDER;
  orientation?: ORIENTATION;
}

我尝试动态删除键的代码:

  async getAllImages(inputParams: QUERY_PARAMS) {
     for (let key in inputParams) {
       if (!inputParams[key]) {
         delete inputParams[key]
       }
     }
     // ...
  }

它抛出错误:

element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'QUERY_PARAMS'. No index signature with a parameter of type 'string' was found on type 'QUERY_PARAMS'

Answer 1

该错误是因为 key 是一个字符串，它不够具体，无法作为 inputParams 的属性，即 keyof QUERY_PARAMS。目前 TS 不允许您为 for 循环 ( issue#3500 ) 的迭代变量定义类型，但您可以对循环内的键执行类型断言:

export interface QUERY_PARAMS {
  query: string;
  min_height?: string;
  // ...
}

async function getAllImages(inputParams: QUERY_PARAMS) {
  for (let key in inputParams) {
    const k = key as keyof QUERY_PARAMS; // <-- type assertion
    if (!inputParams[k]) {
      delete inputParams[k]
    }
  }

  // ...
}

const p: QUERY_PARAMS = {
  query: 's',
  min_height: undefined,
}

console.log(p); // { query: 's', min_height: undefined }

getAllImages(p);

console.log(p); // { query: 's' }