Added helper types

Author: halvardssm

types/mod.ts

@@ -6,11 +6,47 @@ export type FlipMap<T extends Record<keyof T, keyof any>> = {
   [K in keyof T as T[K]]: K;
 };
 
+/**
+ * Make properties K in T optional
+ */
+export type PartialBy<T, K extends keyof T> = Omit<T, K> & Partial<Pick<T, K>>;
+
+/**
+ * Make properties K in T required
+ */
+export type RequiredBy<T, K extends keyof T> =
+  & Omit<T, K>
+  & Required<Pick<T, K>>;
+
+/**
+ * Make properties K in T required, and the rest partial
+ */
+export type RequiredPartialBy<T, K extends keyof T> =
+  & RequiredBy<
+    Pick<T, K>,
+    K
+  >
+  & Partial<Omit<T, K>>;
+
+/**
+ * Make properties K in T readonly
+ */
+export type ReadonlyBy<T, K extends keyof T> =
+  & Omit<T, K>
+  & Readonly<Pick<T, K>>;
+
 /**
  * Makes an object with readonly properties writable
  */
 export type Writeable<T> = { -readonly [P in keyof T]: T[P] };
 
+/**
+ * Make properties K in T writable
+ */
+export type WriteableBy<T, K extends keyof T> =
+  & Omit<T, K>
+  & Writeable<Pick<T, K>>;
+
 /**
  * Gets the values of an object
  */