diff --git a/src/actions/completion.js b/src/actions/completion.js
new file mode 100644
index 0000000..1ffb025
--- /dev/null
+++ b/src/actions/completion.js
@@ -0,0 +1,22 @@
+import actions from '../actions';
+
+const setItems = (groups) => {
+  return {
+    type: actions.COMPLETION_SET_ITEMS,
+    groups,
+  };
+};
+
+const selectNext = () => {
+  return {
+    type: actions.COMPLETION_SELECT_NEXT
+  };
+};
+
+const selectPrev = () => {
+  return {
+    type: actions.COMPLETION_SELECT_PREV
+  };
+};
+
+export { setItems, selectNext, selectPrev };
diff --git a/src/actions/index.js b/src/actions/index.js
index 7b79864..2aa28fa 100644
--- a/src/actions/index.js
+++ b/src/actions/index.js
@@ -9,4 +9,9 @@ export default {
   INPUT_KEY_PRESS: 'input.key,press',
   INPUT_CLEAR_KEYS: 'input.clear.keys',
   INPUT_SET_KEYMAPS: 'input.set,keymaps',
+
+  // Completion
+  COMPLETION_SET_ITEMS: 'completion.set.items',
+  COMPLETION_SELECT_NEXT: 'completions.select.next',
+  COMPLETION_SELECT_PREV: 'completions.select.prev'
 };
diff --git a/src/components/completion.js b/src/components/completion.js
new file mode 100644
index 0000000..e6ee0cb
--- /dev/null
+++ b/src/components/completion.js
@@ -0,0 +1,55 @@
+export default class Completion {
+  constructor(wrapper, store) {
+    this.wrapper = wrapper;
+    this.store = store;
+  }
+
+  update() {
+    let state = this.store.getState();
+
+    this.wrapper.innerHTML = '';
+
+    for (let i = 0; i < state.groups.length; ++i) {
+      let group = state.groups[i];
+      let title = this.createCompletionTitle(group.name);
+      this.wrapper.append(title);
+
+      for (let j = 0; j < group.items.length; ++j) {
+        let item = group.items[j];
+        let li = this.createCompletionItem(item.icon, item.caption, item.url);
+        this.wrapper.append(li);
+
+        if (i === state.groupSelection && j === state.itemSelection) {
+          li.classList.add('vimvixen-completion-selected');
+        }
+      }
+    }
+  }
+
+  createCompletionTitle(text) {
+    let doc = this.wrapper.ownerDocument;
+    let li = doc.createElement('li');
+    li.className = 'vimvixen-console-completion-title';
+    li.textContent = text;
+    return li;
+  }
+
+  createCompletionItem(icon, caption, url) {
+    let doc = this.wrapper.ownerDocument;
+
+    let captionEle = doc.createElement('span');
+    captionEle.className = 'vimvixen-console-completion-item-caption';
+    captionEle.textContent = caption;
+
+    let urlEle = doc.createElement('span');
+    urlEle.className = 'vimvixen-console-completion-item-url';
+    urlEle.textContent = url;
+
+    let li = doc.createElement('li');
+    li.style.backgroundImage = 'url(' + icon + ')';
+    li.className = 'vimvixen-console-completion-item';
+    li.append(captionEle);
+    li.append(urlEle);
+    return li;
+  }
+}
diff --git a/src/pages/completion.js b/src/pages/completion.js
deleted file mode 100644
index 4c69afb..0000000
--- a/src/pages/completion.js
+++ /dev/null
@@ -1,27 +0,0 @@
-export default class Completion {
-  constructor(completions) {
-    if (typeof completions.length !== 'number') {
-      throw new TypeError('completions does not have a length in number');
-    }
-    this.completions = completions;
-    this.index = 0;
-  }
-
-  prev() {
-    let length = this.completions.length;
-    if (length === 0) {
-      return null;
-    }
-    this.index = (this.index + length - 1) % length;
-    return this.completions[this.index];
-  }
-
-  next() {
-    if (this.completions.length === 0) {
-      return null;
-    }
-    let item = this.completions[this.index];
-    this.index = (this.index + 1) % this.completions.length;
-    return item;
-  }
-}
diff --git a/src/pages/console.js b/src/pages/console.js
index 31f2643..40e713e 100644
--- a/src/pages/console.js
+++ b/src/pages/console.js
@@ -1,61 +1,41 @@
 import './console.scss';
-import Completion from './completion';
 import messages from '../content/messages';
+import CompletionComponent from '../components/completion';
+import completionReducer from '../reducers/completion';
+import * as store from '../store';
+import * as completionActions from '../actions/completion';
+
+const completionStore = store.createStore(completionReducer);
+let completionComponent = null;
+
+window.addEventListener('load', () => {
+  let wrapper = document.querySelector('#vimvixen-console-completion');
+  completionComponent = new CompletionComponent(wrapper, completionStore);
+});
 
 // TODO consider object-oriented
 let prevValue = '';
-let completion = null;
 let completionOrigin = '';
 let prevState = {};
 
-const handleBlur = () => {
-  return browser.runtime.sendMessage({
-    type: messages.CONSOLE_BLURRED,
-  });
-};
-
-const selectCompletion = (target) => {
-  let container = window.document.querySelector('#vimvixen-console-completion');
-  Array.prototype.forEach.call(container.children, (ele) => {
-    if (!ele.classList.contains('vimvixen-console-completion-item')) {
-      return;
-    }
-    if (ele === target) {
-      ele.classList.add('vimvixen-completion-selected');
-    } else {
-      ele.classList.remove('vimvixen-completion-selected');
-    }
-  });
-};
-
-const completeNext = () => {
-  if (!completion) {
-    return;
-  }
-  let item = completion.next();
-  if (!item) {
-    return;
-  }
+completionStore.subscribe(() => {
+  completionComponent.update();
 
+  let state = completionStore.getState();
   let input = window.document.querySelector('#vimvixen-console-command-input');
-  input.value = completionOrigin + ' ' + item[0].content;
 
-  selectCompletion(item[1]);
-};
-
-const completePrev = () => {
-  if (!completion) {
-    return;
+  if (state.groupSelection >= 0) {
+    let item = state.groups[state.groupSelection].items[state.itemSelection];
+    input.value = completionOrigin + ' ' + item.content;
+  } else if (state.groups.length > 0) {
+    input.value = completionOrigin + ' ';
   }
-  let item = completion.prev();
-  if (!item) {
-    return;
-  }
-
-  let input = window.document.querySelector('#vimvixen-console-command-input');
-  input.value = completionOrigin + ' ' + item[0].content;
+});
 
-  selectCompletion(item[1]);
+const handleBlur = () => {
+  return browser.runtime.sendMessage({
+    type: messages.CONSOLE_BLURRED,
+  });
 };
 
 const handleKeydown = (e) => {
@@ -71,9 +51,9 @@ const handleKeydown = (e) => {
     });
   case KeyboardEvent.DOM_VK_TAB:
     if (e.shiftKey) {
-      completePrev();
+      completionStore.dispatch(completionActions.selectPrev());
     } else {
-      completeNext();
+      completionStore.dispatch(completionActions.selectNext());
     }
     e.stopPropagation();
     e.preventDefault();
@@ -102,52 +82,10 @@ window.addEventListener('load', () => {
   input.addEventListener('keyup', handleKeyup);
 });
 
-const createCompletionTitle = (text) => {
-  let li = document.createElement('li');
-  li.className = 'vimvixen-console-completion-title';
-  li.textContent = text;
-  return li;
-};
-
-const createCompletionItem = (icon, caption, url) => {
-  let captionEle = document.createElement('span');
-  captionEle.className = 'vimvixen-console-completion-item-caption';
-  captionEle.textContent = caption;
-
-  let urlEle = document.createElement('span');
-  urlEle.className = 'vimvixen-console-completion-item-url';
-  urlEle.textContent = url;
-
-  let li = document.createElement('li');
-  li.style.backgroundImage = 'url(' + icon + ')';
-  li.className = 'vimvixen-console-completion-item';
-  li.append(captionEle);
-  li.append(urlEle);
-  return li;
-};
-
 const updateCompletions = (completions) => {
-  let completionsContainer =
-    window.document.querySelector('#vimvixen-console-completion');
-  let input = window.document.querySelector('#vimvixen-console-command-input');
-
-  completionsContainer.innerHTML = '';
-
-  let pairs = [];
-
-  for (let group of completions) {
-    let title = createCompletionTitle(group.name);
-    completionsContainer.append(title);
+  completionStore.dispatch(completionActions.setItems(completions));
 
-    for (let item of group.items) {
-      let li = createCompletionItem(item.icon, item.caption, item.url);
-      completionsContainer.append(li);
-
-      pairs.push([item, li]);
-    }
-  }
-
-  completion = new Completion(pairs);
+  let input = window.document.querySelector('#vimvixen-console-command-input');
   completionOrigin = input.value.split(' ')[0];
 };
 
diff --git a/src/reducers/completion.js b/src/reducers/completion.js
new file mode 100644
index 0000000..a706988
--- /dev/null
+++ b/src/reducers/completion.js
@@ -0,0 +1,61 @@
+import actions from '../actions';
+
+const defaultState = {
+  groupSelection: -1,
+  itemSelection: -1,
+  groups: [],
+};
+
+const nextSelection = (state) => {
+  if (state.groupSelection < 0) {
+    return [0, 0];
+  }
+
+  let group = state.groups[state.groupSelection];
+  if (state.groupSelection + 1 >= state.groups.length &&
+    state.itemSelection + 1 >= group.items.length) {
+    return [-1, -1];
+  }
+  if (state.itemSelection + 1 >= group.items.length) {
+    return [state.groupSelection + 1, 0];
+  }
+  return [state.groupSelection, state.itemSelection + 1];
+};
+
+const prevSelection = (state) => {
+  if (state.groupSelection < 0) {
+    return [0, 0];
+  }
+  if (state.groupSelection === 0 && state.itemSelection === 0) {
+    return [-1, -1];
+  } else if (state.itemSelection === 0) {
+    return [
+      state.groupSelection - 1,
+      state.groups[state.groupSelection - 1].items.length - 1
+    ];
+  }
+  return [state.groupSelection, state.itemSelection - 1];
+};
+
+export default function reducer(state = defaultState, action = {}) {
+  switch (action.type) {
+  case actions.COMPLETION_SET_ITEMS:
+    return Object.assign({}, state, {
+      groups: action.groups
+    });
+  case actions.COMPLETION_SELECT_NEXT: {
+    let next = nextSelection(state);
+    return Object.assign({}, state, {
+      groupSelection: next[0],
+      itemSelection: next[1],
+    });
+  }
+  case actions.COMPLETION_SELECT_PREV: {
+    let next = prevSelection(state);
+    return Object.assign({}, state, {
+      groupSelection: next[0],
+      itemSelection: next[1],
+    });
+  }
+  }
+}
diff --git a/test/pages/completion.test.js b/test/pages/completion.test.js
deleted file mode 100644
index 28dd9a7..0000000
--- a/test/pages/completion.test.js
+++ /dev/null
@@ -1,48 +0,0 @@
-import { expect } from "chai";
-import Completion from '../../src/pages/completion';
-
-describe('Completion class', () => {
-  describe('#constructor', () => {
-    it('creates new object by iterable items', () => {
-      new Completion([1,2,3,4,5]);
-      new Completion([]);
-      new Completion('hello');
-      new Completion('');
-    });
-
-    it('creates new object by iterable items', () => {
-      expect(() => new Completion({ key: 'value' })).to.throw(TypeError);
-      expect(() => new Completion(12345)).to.throw(TypeError);
-    });
-  });
-
-  describe('#next', () => {
-    it('complete next items', () => {
-      let completion = new Completion([3, 4, 5]);
-      expect(completion.next()).to.equal(3);
-      expect(completion.next()).to.equal(4);
-      expect(completion.next()).to.equal(5);
-      expect(completion.next()).to.equal(3);
-    });
-
-    it('returns null when empty completions', () => {
-      let completion = new Completion([]);
-      expect(completion.next()).to.be.null;
-    });
-  });
-
-  describe('#prev', () => {
-    it('complete prev items', () => {
-      let completion = new Completion([3, 4, 5]);
-      expect(completion.prev()).to.equal(5);
-      expect(completion.prev()).to.equal(4);
-      expect(completion.prev()).to.equal(3);
-      expect(completion.prev()).to.equal(5);
-    });
-
-    it('returns null when empty completions', () => {
-      let completion = new Completion([]);
-      expect(completion.prev()).to.be.null;
-    });
-  });
-});