[Typescript] Filtering properties out

List all the props with begin with "query" key in Document

type queryTypes = Extract<keyof Document, `query${string}`>
type queryyPoprDoc = {
  [Key in queryTypes]: Document[Key]
}

What if we want to filter out by value?
For example we want to get all the methods which return Element | Element[].

Idea:

1. Construct kind of object:

{
 querySelector: "querySelector",
 alinkColor: never
 ..
}

2. So in the object type, anything which return Element | Element[], will keep the key as string, otherwise will assign never type.

3. Get all the string value out of the object type

type FilteredKeys<TValue, Condition> = {
  [K in keyof TValue]: TValue[K] extends Condition ? K: never
}[keyof TValue] & keyof Document
type RelevantDocumentKeys = FilteredKeys<Document, (...args: any[]) => Element | Element[]>
type ValueFilteredDoc = Pick<Document, RelevantDocumentKeys>
function load(doc: ValueFilteredDoc) {
  doc.querySelector("input")
}

标签：Typescript,never,Element,keyof,Document,type,properties,out
来源： https://www.cnblogs.com/Answer1215/p/16609164.html