#utility-types

TypeScriptintermediate

Extract and Exclude in a tiny parser helper

type Assignment = { kind: "assign"; key: string; value: string };
type Flag = { kind: "flag"; key: string };
type Token = Assignment | Flag | { kind: "comment"; text: string };

const tokenize = (line: string): Token => {

Use utility conditional types to parse and narrow a small input grammar.

TypeScriptadvanced

Building DeepPartial<T> from scratch

export type DeepPartial<T> = T extends readonly unknown[]
  ? T
  : T extends object
    ? { [K in keyof T]?: DeepPartial<T[K]> }
    : T;

Make every property optional at every nesting level, for patch-style updates, without touching arrays element by element.