[6팀 정용준] Chapter 1-3. React, Beyond the Basics

packages/lib/src/equals/deepEquals.ts

@@ -1,3 +1,34 @@
+import { getObjectKeys, isArray, isObject, isPrimitive } from "./utils";
+
 export const deepEquals = (a: unknown, b: unknown) => {
+  if (typeof a !== typeof b) return false;
+
+  if (isPrimitive(a) && isPrimitive(b)) {
+    return a === b;
+  }
+
+  if (isArray(a) && isArray(b)) {
+    if (a.length !== b.length) return false;
+
+    for (let i = 0; i < a.length; i++) {
+      if (!deepEquals(a[i], b[i])) return false;
+    }
+
+    return true;
+  }
+
+  if (isObject(a) && isObject(b)) {
+    const keysA = getObjectKeys(a);
+    const keysB = getObjectKeys(b);
+
+    if (keysA.length !== keysB.length) return false;
+
+    for (const key of keysA) {
+      if (!deepEquals(a[key], b[key])) return false;
+    }
+
+    return true;
+  }
+
   return a === b;
 };

packages/lib/src/equals/shallowEquals.ts

@@ -1,3 +1,34 @@
+import { getObjectKeys, isArray, isObject, isPrimitive } from "./utils";
+
 export const shallowEquals = (a: unknown, b: unknown) => {
+  if (typeof a !== typeof b) return false;
+
+  if (isPrimitive(a) && isPrimitive(b)) {
+    return a === b;
+  }
+
+  if (isArray(a) && isArray(b)) {
+    if (a.length !== b.length) return false;
+
+    for (let i = 0; i < a.length; i++) {
+      if (a[i] !== b[i]) return false;
+    }
+
+    return true;
+  }
+
+  if (isObject(a) && isObject(b)) {
+    const keysA = getObjectKeys(a);
+    const keysB = getObjectKeys(b);
+
+    if (keysA.length !== keysB.length) return false;
+
+    for (const key of keysA) {
+      if (a[key] !== b[key]) return false;
+    }
+
+    return true;
+  }
+
   return a === b;
 };

packages/lib/src/equals/utils.ts

@@ -0,0 +1,9 @@
+export type Primitive = string | number | boolean | null | undefined | bigint | symbol;
+
+export const isArray = (value: unknown): value is unknown[] => Array.isArray(value);
+
+export const isObject = (value: unknown): value is object => typeof value === "object" && value !== null;
+
+export const isPrimitive = (value: unknown): value is Primitive => typeof value !== "object" || value === null;
+
+export const getObjectKeys = <T extends object>(o: T): (keyof T)[] => Object.keys(o) as (keyof T)[];