Replace<String, Pattern, Replacement>

Overview

The Replace<String, Pattern, Replacement> is a utility type that replaces the first occurrence of a specified pattern in a string with a given replacement string.

Syntax

export type Replace<
  S extends string,
  Pattern extends string,
  Replacement extends string,
> = S extends `${infer Head}${Pattern}${infer Tail}`
  ? `${Head}${Replacement}${Tail}`
  : S;

• String (S) : The string in which the replacement will be made.
• Pattern : The substring pattern to be replaced.
• Replacement : The substring that will replace the pattern.

Examples

Example #1

type T0 = Replace<'hello world', 'world', 'typescript'>; // 'hello typescript'
type T1 = Replace<'bar bar baz', 'bar', 'foo'>; // 'foo bar baz'
type T2 = Replace<'', 'pattern', 'replacement'>; // ''

Example #2

type FieldTemplate = '{fieldName}_field';
type FieldPlaceholder = '{fieldName}';

type FieldName = 'username' | 'password';
type FieldNames = Replace<FieldTemplate, FieldPlaceholder, FieldName>;
// FieldNames = 'username_field' | 'password_field';