groupBy是TypeScript安全的 [英] groupBy that is TypeScript safe

问题描述

给出所有已经存在的答案，我们尝试创建一个不抱怨TypeScript错误的 groupBy 箭头函数.在

使用的键确实有可能为空/空白.因此，TypeScript在这里并没有错.因此，在那种情况下，它应该简单地使用占位符，例如 NA 或类似的东西.

为此 groupBy 函数创建可重用的无错误打字稿版本的正确方法是什么?

解决方案

使用一些泛型来降低键类型并强制对象包含键:

  type ObjectKey =字符串|编号|象征;const groupBy =< K扩展ObjectKey，TItem扩展Record< K，ObjectKey>>(项目:TItem []，键:K):Record< ObjectKey，TItem []>=>items.reduce((结果，项目)=>({...结果，[item [key]]:[...(结果[item [key]] || [])，项目]，})，{}作为Record< ObjectKey，TItem []>); 

游乐场链接

Given all the answers already out there we tried to create a groupBy arrow function that doesn't complain about TypeScript errors. with guidance from this answer and this one we already have this working code:

const groupBy = <TItem>(
  items: TItem[],
  key: string
): { [key: string]: TItem[] } =>
  items.reduce(
    (result, item) => ({
      ...result,
      [item[key]]: [...(result[item[key]] || []), item],
    }),
    {}
  )

However, it still complains:

It is indeed possible that the used key is empty/blank. So TypeScript is not wrong here. So in that case it should simply use a placeholder value like NA or something.

What is the correct way to create a reusable error free typescript version for this groupBy function?

解决方案

Use some generics to lower down the key type and force the object to contain the key:

type ObjectKey = string | number | symbol;

const groupBy = <K extends ObjectKey, TItem extends Record<K, ObjectKey>>(
  items: TItem[],
  key: K
): Record<ObjectKey, TItem[]> =>
  items.reduce(
    (result, item) => ({
      ...result,
      [item[key]]: [...(result[item[key]] || []), item],
    }),
    {} as Record<ObjectKey, TItem[]>
  );

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