diff --git a/packages/core/src/api/callbacks.ts b/packages/core/src/api/callbacks.ts
index c771373..3d71115 100644
--- a/packages/core/src/api/callbacks.ts
+++ b/packages/core/src/api/callbacks.ts
@@ -49,7 +49,7 @@ export function updateCallbacks(storage: IconStorageWithAPI): void {
 					}
 
 					const name = icon.name;
-					if (storage.icons[name] !== void 0) {
+					if (storage.icons[name]) {
 						// Loaded
 						icons.loaded.push({
 							provider,
diff --git a/packages/core/src/api/modules/mock.ts b/packages/core/src/api/modules/mock.ts
index 9c75da8..0ec8e3c 100644
--- a/packages/core/src/api/modules/mock.ts
+++ b/packages/core/src/api/modules/mock.ts
@@ -109,35 +109,45 @@ export function mockAPIData(data: IconifyMockAPI): void {
 	switch (data.type) {
 		case 'icons': {
 			const provider = data.provider;
-			if (iconsStorage[provider] === void 0) {
-				iconsStorage[provider] = {};
-			}
-			const providerStorage = iconsStorage[provider];
-
 			const prefix = data.prefix;
-			if (providerStorage[prefix] === void 0) {
-				providerStorage[prefix] = [];
-			}
 
-			iconsStorage[provider][prefix].push(data);
+			const providerStorage =
+				iconsStorage[provider] ||
+				(iconsStorage[provider] = Object.create(null) as Record<
+					string,
+					IconifyMockIconsAPI[]
+				>);
+
+			(providerStorage[prefix] || (providerStorage[prefix] = [])).push(
+				data
+			);
 			break;
 		}
 
 		case 'custom': {
 			const provider = data.provider;
-			if (customProviderStorage[provider] === void 0) {
-				customProviderStorage[provider] = {};
-			}
-			customProviderStorage[provider][data.uri] = data;
+
+			const providerStorage =
+				customProviderStorage[provider] ||
+				(customProviderStorage[provider] = Object.create(
+					null
+				) as Record<string, IconifyMockCustomAPI>);
+
+			providerStorage[data.uri] = data;
 			break;
 		}
 
 		case 'host': {
 			const host = data.host;
-			if (customHostStorage[host] === void 0) {
-				customHostStorage[host] = {};
-			}
-			customHostStorage[host][data.uri] = data;
+
+			const hostStorage =
+				customHostStorage[host] ||
+				(customHostStorage[host] = Object.create(null) as Record<
+					string,
+					IconifyMockCustomHostAPI
+				>);
+
+			hostStorage[data.uri] = data;
 			break;
 		}
 	}
diff --git a/packages/core/src/api/query.ts b/packages/core/src/api/query.ts
index d00fd72..a834904 100644
--- a/packages/core/src/api/query.ts
+++ b/packages/core/src/api/query.ts
@@ -38,7 +38,7 @@ const redundancyCache = Object.create(null) as Record<
 function getRedundancyCache(
 	provider: string
 ): IconifyAPIInternalStorage | undefined {
-	if (redundancyCache[provider] === void 0) {
+	if (!redundancyCache[provider]) {
 		const config = getAPIConfig(provider);
 		if (!config) {
 			// Configuration is not set!
diff --git a/packages/core/src/browser-storage/mock.ts b/packages/core/src/browser-storage/mock.ts
index 014b1d9..420f980 100644
--- a/packages/core/src/browser-storage/mock.ts
+++ b/packages/core/src/browser-storage/mock.ts
@@ -41,7 +41,7 @@ export class Storage {
 		if (!this.canRead) {
 			throw new Error('Restricted storage');
 		}
-		return this.items[name] === void 0 ? null : this.items[name];
+		return name in this.items ? this.items[name] : null;
 	}
 
 	/**
diff --git a/packages/core/src/icon/sort.ts b/packages/core/src/icon/sort.ts
index f042bdf..01e7aae 100644
--- a/packages/core/src/icon/sort.ts
+++ b/packages/core/src/icon/sort.ts
@@ -56,21 +56,19 @@ export function sortIcons(icons: IconifyIconName[]): SortedIcons {
 		const prefix = icon.prefix;
 		const name = icon.name;
 
-		if (storage[provider] === void 0) {
-			storage[provider] = Object.create(null) as Record<
+		const providerStorage =
+			storage[provider] ||
+			(storage[provider] = Object.create(null) as Record<
 				string,
 				IconStorage
-			>;
-		}
-		const providerStorage = storage[provider];
+			>);
 
-		if (providerStorage[prefix] === void 0) {
-			providerStorage[prefix] = getStorage(provider, prefix);
-		}
-		const localStorage = providerStorage[prefix];
+		const localStorage =
+			providerStorage[prefix] ||
+			(providerStorage[prefix] = getStorage(provider, prefix));
 
 		let list;
-		if (localStorage.icons[name] !== void 0) {
+		if (name in localStorage.icons) {
 			list = result.loaded;
 		} else if (prefix === '' || localStorage.missing.has(name)) {
 			// Mark icons without prefix as missing because they cannot be loaded from API