diff --git a/src/client/app/common/scripts/streaming/stream-manager.ts b/src/client/app/common/scripts/streaming/stream-manager.ts
index 568b8b037..8dd06f67d 100644
--- a/src/client/app/common/scripts/streaming/stream-manager.ts
+++ b/src/client/app/common/scripts/streaming/stream-manager.ts
@@ -1,6 +1,7 @@
 import { EventEmitter } from 'eventemitter3';
 import * as uuid from 'uuid';
 import Connection from './stream';
+import { erase } from '../../../../../prelude/array';
 
 /**
  * ストリーム接続を管理するクラス
@@ -89,7 +90,7 @@ export default abstract class StreamManager<T extends Connection> extends EventE
 	 * @param userId use で発行したユーザーID
 	 */
 	public dispose(userId) {
-		this.users = this.users.filter(id => id != userId);
+		this.users = erase(userId, this.users);
 
 		this._connection.user = `Managed (${ this.users.length })`;
 
diff --git a/src/client/app/common/views/components/poll-editor.vue b/src/client/app/common/views/components/poll-editor.vue
index 115c934c8..30d9799fe 100644
--- a/src/client/app/common/views/components/poll-editor.vue
+++ b/src/client/app/common/views/components/poll-editor.vue
@@ -20,6 +20,7 @@
 
 <script lang="ts">
 import Vue from 'vue';
+import { erase } from '../../../../../prelude/array';
 export default Vue.extend({
 	data() {
 		return {
@@ -53,7 +54,7 @@ export default Vue.extend({
 
 		get() {
 			return {
-				choices: this.choices.filter(choice => choice != '')
+				choices: erase('', this.choices)
 			}
 		},
 
diff --git a/src/client/app/desktop/views/components/post-form.vue b/src/client/app/desktop/views/components/post-form.vue
index f6f52c8f1..65dc9eb9c 100644
--- a/src/client/app/desktop/views/components/post-form.vue
+++ b/src/client/app/desktop/views/components/post-form.vue
@@ -62,6 +62,7 @@ import getFace from '../../../common/scripts/get-face';
 import MkVisibilityChooser from '../../../common/views/components/visibility-chooser.vue';
 import parse from '../../../../../mfm/parse';
 import { host } from '../../../config';
+import { erase } from '../../../../../prelude/array';
 
 export default Vue.extend({
 	components: {
@@ -346,7 +347,7 @@ export default Vue.extend({
 		},
 
 		removeVisibleUser(user) {
-			this.visibleUsers = this.visibleUsers.filter(u => u != user);
+			this.visibleUsers = erase(user, this.visibleUsers);
 		},
 
 		post() {
diff --git a/src/client/app/mios.ts b/src/client/app/mios.ts
index c2ec7f175..0f72cd2f3 100644
--- a/src/client/app/mios.ts
+++ b/src/client/app/mios.ts
@@ -17,6 +17,7 @@ import Err from './common/views/components/connect-failed.vue';
 import { LocalTimelineStreamManager } from './common/scripts/streaming/local-timeline';
 import { HybridTimelineStreamManager } from './common/scripts/streaming/hybrid-timeline';
 import { GlobalTimelineStreamManager } from './common/scripts/streaming/global-timeline';
+import { erase } from '../../prelude/array';
 
 //#region api requests
 let spinner = null;
@@ -537,7 +538,7 @@ export default class MiOS extends EventEmitter {
 	}
 
 	public unregisterStreamConnection(connection: Connection) {
-		this.connections = this.connections.filter(c => c != connection);
+		this.connections = erase(connection, this.connections);
 	}
 }
 
diff --git a/src/client/app/mobile/views/components/post-form.vue b/src/client/app/mobile/views/components/post-form.vue
index 644e27cce..8107c1f3a 100644
--- a/src/client/app/mobile/views/components/post-form.vue
+++ b/src/client/app/mobile/views/components/post-form.vue
@@ -59,6 +59,7 @@ import MkVisibilityChooser from '../../../common/views/components/visibility-cho
 import getFace from '../../../common/scripts/get-face';
 import parse from '../../../../../mfm/parse';
 import { host } from '../../../config';
+import { erase } from '../../../../../prelude/array';
 
 export default Vue.extend({
 	components: {
@@ -262,7 +263,7 @@ export default Vue.extend({
 		},
 
 		removeVisibleUser(user) {
-			this.visibleUsers = this.visibleUsers.filter(u => u != user);
+			this.visibleUsers = erase(user, this.visibleUsers);
 		},
 
 		clear() {
diff --git a/src/client/app/store.ts b/src/client/app/store.ts
index 53f3eefc0..08dd9f992 100644
--- a/src/client/app/store.ts
+++ b/src/client/app/store.ts
@@ -4,6 +4,7 @@ import * as nestedProperty from 'nested-property';
 
 import MiOS from './mios';
 import { hostname } from './config';
+import { erase } from '../../prelude/array';
 
 const defaultSettings = {
 	home: null,
@@ -195,7 +196,7 @@ export default (os: MiOS) => new Vuex.Store({
 
 				removeDeckColumn(state, id) {
 					state.deck.columns = state.deck.columns.filter(c => c.id != id);
-					state.deck.layout = state.deck.layout.map(ids => ids.filter(x => x != id));
+					state.deck.layout = state.deck.layout.map(ids => erase(id, ids));
 					state.deck.layout = state.deck.layout.filter(ids => ids.length > 0);
 				},
 
@@ -266,7 +267,7 @@ export default (os: MiOS) => new Vuex.Store({
 
 				stackLeftDeckColumn(state, id) {
 					const i = state.deck.layout.findIndex(ids => ids.indexOf(id) != -1);
-					state.deck.layout = state.deck.layout.map(ids => ids.filter(x => x != id));
+					state.deck.layout = state.deck.layout.map(ids => erase(id, ids));
 					const left = state.deck.layout[i - 1];
 					if (left) state.deck.layout[i - 1].push(id);
 					state.deck.layout = state.deck.layout.filter(ids => ids.length > 0);
@@ -274,7 +275,7 @@ export default (os: MiOS) => new Vuex.Store({
 
 				popRightDeckColumn(state, id) {
 					const i = state.deck.layout.findIndex(ids => ids.indexOf(id) != -1);
-					state.deck.layout = state.deck.layout.map(ids => ids.filter(x => x != id));
+					state.deck.layout = state.deck.layout.map(ids => erase(id, ids));
 					state.deck.layout.splice(i + 1, 0, [id]);
 					state.deck.layout = state.deck.layout.filter(ids => ids.length > 0);
 				},
diff --git a/src/client/app/sw.js b/src/client/app/sw.js
index ac7ea20ac..d381bfb7a 100644
--- a/src/client/app/sw.js
+++ b/src/client/app/sw.js
@@ -3,6 +3,7 @@
  */
 
 import composeNotification from './common/scripts/compose-notification';
+import { erase } from '../../prelude/array';
 
 // キャッシュするリソース
 const cachee = [
@@ -24,8 +25,7 @@ self.addEventListener('activate', ev => {
 	// Clean up old caches
 	ev.waitUntil(
 		caches.keys().then(keys => Promise.all(
-			keys
-				.filter(key => key != _VERSION_)
+			erase(_VERSION_, keys)
 				.map(key => caches.delete(key))
 		))
 	);
diff --git a/src/prelude/array.ts b/src/prelude/array.ts
index 9a3c266d6..a2a6bbd4c 100644
--- a/src/prelude/array.ts
+++ b/src/prelude/array.ts
@@ -13,3 +13,7 @@ export function concat<T>(xss: T[][]): T[] {
 export function intersperse<T>(sep: T, xs: T[]): T[] {
 	return concat(xs.map(x => [sep, x])).slice(1);
 }
+
+export function erase<T>(x: T, xs: T[]): T[] {
+	return xs.filter(y => x !== y);
+}
diff --git a/src/server/api/endpoints/hashtags/trend.ts b/src/server/api/endpoints/hashtags/trend.ts
index 01dfccc71..e7c08ca9f 100644
--- a/src/server/api/endpoints/hashtags/trend.ts
+++ b/src/server/api/endpoints/hashtags/trend.ts
@@ -1,4 +1,5 @@
 import Note from '../../../../models/note';
+import { erase } from '../../../../prelude/array';
 
 /*
 トレンドに載るためには「『直近a分間のユニーク投稿数が今からa分前～今からb分前の間のユニーク投稿数のn倍以上』のハッシュタグの上位5位以内に入る」ことが必要
@@ -85,8 +86,7 @@ export default () => new Promise(async (res, rej) => {
 	//#endregion
 
 	// タグを人気順に並べ替え
-	let hots = (await Promise.all(hotsPromises))
-		.filter(x => x != null)
+	let hots = erase(null, await Promise.all(hotsPromises))
 		.sort((a, b) => b.count - a.count)
 		.map(tag => tag.name)
 		.slice(0, max);
diff --git a/src/server/api/endpoints/notes/search_by_tag.ts b/src/server/api/endpoints/notes/search_by_tag.ts
index 82f11a977..77082c260 100644
--- a/src/server/api/endpoints/notes/search_by_tag.ts
+++ b/src/server/api/endpoints/notes/search_by_tag.ts
@@ -5,6 +5,7 @@ import Mute from '../../../../models/mute';
 import { getFriendIds } from '../../common/get-friends';
 import { pack } from '../../../../models/note';
 import getParams from '../../get-params';
+import { erase } from '../../../../prelude/array';
 
 export const meta = {
 	desc: {
@@ -103,23 +104,23 @@ export default (params: any, me: ILocalUser) => new Promise(async (res, rej) =>
 	if (psErr) throw psErr;
 
 	if (ps.includeUserUsernames != null) {
-		const ids = (await Promise.all(ps.includeUserUsernames.map(async (username) => {
+		const ids = erase(null, await Promise.all(ps.includeUserUsernames.map(async (username) => {
 			const _user = await User.findOne({
 				usernameLower: username.toLowerCase()
 			});
 			return _user ? _user._id : null;
-		}))).filter(id => id != null);
+		})));
 
 		ids.forEach(id => ps.includeUserIds.push(id));
 	}
 
 	if (ps.excludeUserUsernames != null) {
-		const ids = (await Promise.all(ps.excludeUserUsernames.map(async (username) => {
+		const ids = erase(null, await Promise.all(ps.excludeUserUsernames.map(async (username) => {
 			const _user = await User.findOne({
 				usernameLower: username.toLowerCase()
 			});
 			return _user ? _user._id : null;
-		}))).filter(id => id != null);
+		})));
 
 		ids.forEach(id => ps.excludeUserIds.push(id));
 	}
diff --git a/src/services/note/create.ts b/src/services/note/create.ts
index 11e375586..4759497c6 100644
--- a/src/services/note/create.ts
+++ b/src/services/note/create.ts
@@ -24,6 +24,7 @@ import isQuote from '../../misc/is-quote';
 import { TextElementMention } from '../../mfm/parse/elements/mention';
 import { TextElementHashtag } from '../../mfm/parse/elements/hashtag';
 import { updateNoteStats } from '../update-chart';
+import { erase } from '../../prelude/array';
 
 type NotificationType = 'reply' | 'renote' | 'quote' | 'mention';
 
@@ -103,7 +104,7 @@ export default async (user: IUser, data: Option, silent = false) => new Promise<
 	if (data.viaMobile == null) data.viaMobile = false;
 
 	if (data.visibleUsers) {
-		data.visibleUsers = data.visibleUsers.filter(x => x != null);
+		data.visibleUsers = erase(null, data.visibleUsers);
 	}
 
 	if (data.reply && data.reply.deletedAt != null) {
@@ -547,13 +548,13 @@ async function extractMentionedUsers(tokens: ReturnType<typeof parse>): Promise<
 	)];
 
 	const mentionedUsers = [...new Set(
-		(await Promise.all(mentionTokens.map(async m => {
+		erase(null, await Promise.all(mentionTokens.map(async m => {
 			try {
 				return await resolveUser(m.username, m.host);
 			} catch (e) {
 				return null;
 			}
-		}))).filter(x => x != null)
+		})))
 	)];
 
 	return mentionedUsers;