💫 workflow(3-3):

Author: 2495867729

easy/48-Exclude.ts

@@ -3,7 +3,7 @@
  * @Description:Exclude
  */
 
-type Exclude<T, K> = T extends K ? never : T;
+export type Exclude<T, K> = T extends K ? never : T;
 type IType1 = {
     name: string;
     age: number;

medium/02-GetReturnType.ts

@@ -0,0 +1,19 @@
+/*
+ * @Date: 2022-03-03
+ * @Description: Get Retrun Type
+ */
+
+const fn = (v: boolean) => {
+    if (v) return 1;
+    else return 2;
+};
+
+type MyReturnType<T extends (...args: any[]) => any> = T extends (
+    ...args: any[]
+) => infer R
+    ? R
+    : any;
+
+type a = MyReturnType<typeof fn>; // should be "1 | 2"
+
+export {};

medium/03-Omit.ts

@@ -0,0 +1,22 @@
+/*
+ * @Date: 2022-03-03
+ * @Description: Omit
+ */
+
+interface Todo {
+    title: string;
+    description: string;
+    completed: boolean;
+}
+
+type MyOmit<T, K extends string | number | symbol> = {
+    [U in Exclude<keyof T, K>]: false;
+};
+
+type TodoPreview = MyOmit<Todo, "description" | "title">;
+
+const todo: TodoPreview = {
+    completed: false,
+};
+
+export {};

medium/08-Readonly2.ts

@@ -0,0 +1,36 @@
+/*
+ * @Date: 2022-03-03
+ * @Description: Readonly2
+ */
+
+interface Todo {
+    title: string;
+    description: string;
+    completed: boolean;
+}
+
+type MyReadonly2<T, K extends keyof T> = {
+    readonly [P in K]: T[P];
+} & {
+    [L in Exclude<keyof T, K>]: T[L];
+};
+
+const todo: MyReadonly2<Todo, "title" | "description"> = {
+    title: "Hey",
+    description: "foobar",
+    completed: false,
+};
+
+//todo.title = "Hello"; // Error: cannot reassign a readonly property
+//todo.description = "barFoo"; // Error: cannot reassign a readonly property
+todo.completed = true; // OK
+
+export {};
+
+type ReadOnly3<T, K> = K extends keyof T
+    ? {
+          readonly [U in K]: T[U];
+      } & {
+          [L in Exclude<keyof T, K>]: T[L];
+      }
+    : T;

medium/09-DeepReadonly.ts

@@ -0,0 +1,50 @@
+/*
+ * @Date: 2022-03-03
+ * @Description: DeepReadonly
+ */
+
+type X = {
+    x: {
+        a: 1;
+        b: "hi";
+    };
+    y: "hey";
+};
+
+//1
+
+type DeepReadonly<T> = {
+    readonly [P in keyof T]: T[P] extends { [index: string]: unknown }
+        ? DeepReadonly<T[P]>
+        : T[P];
+};
+
+//2
+
+type DeepReadonly2<T> = keyof T extends never
+    ? T
+    : {
+          [P in keyof T]: DeepReadonly2<T[P]>;
+      };
+
+type Expected = {
+    readonly x: {
+        readonly a: 1;
+        readonly b: "hi";
+    };
+    readonly y: "hey";
+};
+
+type Todo = DeepReadonly<X>; // should be same as `Expected`
+
+//判断是否为对象 keyof T extends never  ? :
+// extends {[index;string]:unknown}
+
+const test: Todo = {
+    x: {
+        a: 1,
+        b: "hi",
+    },
+    y: "hey",
+};
+//test.x.a = 123;