keep

Keeps specific character types or substring(s) in a string. See also: strip()

TypeScript

keep(str: string, options: KeepOptions = {}): string

type CharacterType =
  | "letters"
  | "numbers"
  | "spaces"
  | "special"
  | "lowercase"
  | "uppercase"
  | "punctuation"

interface StripOptions {
  types?: CharacterType[]
  custom?: string[]
}

// Example:

keep("hello1234", { type: ["numbers"] }) //=> "1234"
keep("hello1234", { type: ["letters"] }) //=> "hello"
keep("hello, newman!", { type: ["punctuation"] }) //=> ",!"
keep("hello@#$%^", { type: ["special"] }) //=> "@#$%^"
keep("hello newman", { type: ["spaces"] }) //=> " "
keep("hello newman", { custom : ["new", "man"] }) //=> "newman"