OmitByType

In this medium-level challenge, you'll build an OmitByType utility that filters out properties from an object type T whose values are assignable to a given type U.

type OmitBoolean = OmitByType<{
name: string
count: number
isReadonly: boolean
isEnable: boolean
}, boolean> // { name: string; count: number }

interface Model {
  name: string
  count: number
  isReadonly: boolean
  isEnable: boolean
}

type cases = [
  Expect<Equal<OmitByType<Model, boolean>, { name: string; count: number }>>,
  Expect<
    Equal<
      OmitByType<Model, string>,
      { count: number; isReadonly: boolean; isEnable: boolean }
    >
  >,
  Expect<
    Equal<
      OmitByType<Model, number>,
      { name: string; isReadonly: boolean; isEnable: boolean }
    >
  >,
]

Detailed Explanation

type OmitByType<T, U> = {
  [K in keyof T as T[K] extends U ? never : K]: T[K]
}

How it works:

• We iterate over all keys K in T using a mapped type.
• The as clause performs key remapping: for each key, we check if T[K] extends U.
• If the property's type is assignable to U, we remap the key to never, which effectively removes it from the resulting type.
• Otherwise, we keep the key and preserve its original type T[K].

This challenge helps you understand key remapping in mapped types and how to apply conditional filtering of object properties based on their value types in real-world scenarios.