用 JavaScript 实现一个简单的笔记应用程序

记笔记是学习新知识技能比较好的做法。记笔记的一些好处是：记笔记可以作为学习辅助工具，记笔记可以提高注意力和对细节的关注，促进主动学习，并提高记忆力。

记笔记并不一定是写在纸上或书本上，记笔记，可以在我们的手机上通过打字来完成。

本文将提供有关如何使用 HTML5、CSS3 和 JavaScript 构建笔记应用程序的信息。

本文适用于熟悉 HTML5、CSS3 和 JavaScript 基础知识的人。本文不包括对 HTML5、CSS3 和 JavaScript 的详细阐述，但会提供实现源代码。

现在，让我们开始吧首先，我们需要用 HTML5 和 CSS3 创建一个UI界面。

接着，我们需要从iconscout 网站上引入获取图标。

iconscout 网站地址：https://iconscout.com/unicons/explore/line

HTML 的示例代码：

const addBox = document.querySelector('.add-box'),
popupBox = document.querySelector('.popup-box'),
popupTitle = popupBox.querySelector('header p'),
closeIcon = document.querySelector('header i'),
titleEl = document.querySelector('input'),
descEl = document.querySelector('textarea'),
addBtn = document.querySelector('button ');


const months= ['January', 'Febuary', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']

const notes = JSON.parse(localStorage.getItem('notes') || '[]');
let isUpdate = false, updateId;

function showNotes() {
    document.querySelectorAll('.note').forEach(note => note.remove());
    notes.forEach((note, index)=>{
        let liEl=`<li class="note">
                        <div class="details">
                            <p>${note.title}</p>
                            <span>${note.description}</span>
                        </div>
                        <div class="bottom-content">
                            <span>${note.date}</span>
                            <div class="settings">
                                <i onClick="updateNote(${index}, '${note.title}', '${note.description}')"  class="uil uil-edit"></i>
                                <i onClick="deleteNote(${index})" class="uil uil-trash"></i>
                            </div>
                        </div>
                    </li>`;
        addBox.insertAdjacentHTML('afterend', liEl);
    });
}

showNotes();

function deleteNote(noteId) {
    let confirmDelete= confirm("Are you sure you want to delete this note?");
    if(!confirmDelete) return;
    notes.splice(noteId, 1);
    localStorage.setItem('notes', JSON.stringify(notes));
    showNotes();
}

function updateNote(noteId, title, desc) {
    isUpdate = true;
    updateId = noteId;
    addBox.click();
    titleEl.value = title;
    descEl.value = desc;
    addBtn.innerText = 'Edit Note';
    popupTitle.innerText = 'Editing a Note';
}


addBox.addEventListener('click', ()=>{
    titleEl.focus();
    popupBox.classList.add('show')
});

closeIcon.addEventListener('click', ()=>{
    isUpdate = false;
    titleEl.value = '';
    descEl.value = '';
    addBtn.innerText = 'Add Note';
    popupTitle.innerText = 'Add a new Note';
    popupBox.classList.remove('show');
});

addBtn.addEventListener('click', (e)=>{
    e.preventDefault();
    let noteTitle = titleEl.value,
    noteDesc = descEl.value;
    if (noteTitle || noteDesc) {
        let dateEl= new Date(),
        month = months[dateEl.getMonth()],
        day = dateEl.getDate(),
        year = dateEl.getFullYear();


        let noteInfo = {
            title: noteTitle,
            description: noteDesc,
            date: `${month} ${day} ${year}`
        }

        if (!isUpdate) {
            notes.push(noteInfo);
        }else{
            isUpdate = false;
            notes[updateId] = noteInfo;
        }

        localStorage.setItem('notes', JSON.stringify(notes));
        closeIcon.click();
        showNotes();
    }
});

CSS 的示例代码：

const addBox = document.querySelector('.add-box'),
popupBox = document.querySelector('.popup-box'),
popupTitle = popupBox.querySelector('header p'),
closeIcon = document.querySelector('header i'),
titleEl = document.querySelector('input'),
descEl = document.querySelector('textarea'),
addBtn = document.querySelector('button ');


const months= ['January', 'Febuary', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']

const notes = JSON.parse(localStorage.getItem('notes') || '[]');
let isUpdate = false, updateId;

function showNotes() {
    document.querySelectorAll('.note').forEach(note => note.remove());
    notes.forEach((note, index)=>{
        let liEl=`<li class="note">
                        <div class="details">
                            <p>${note.title}</p>
                            <span>${note.description}</span>
                        </div>
                        <div class="bottom-content">
                            <span>${note.date}</span>
                            <div class="settings">
                                <i onClick="updateNote(${index}, '${note.title}', '${note.description}')"  class="uil uil-edit"></i>
                                <i onClick="deleteNote(${index})" class="uil uil-trash"></i>
                            </div>
                        </div>
                    </li>`;
        addBox.insertAdjacentHTML('afterend', liEl);
    });
}

showNotes();

function deleteNote(noteId) {
    let confirmDelete= confirm("Are you sure you want to delete this note?");
    if(!confirmDelete) return;
    notes.splice(noteId, 1);
    localStorage.setItem('notes', JSON.stringify(notes));
    showNotes();
}

function updateNote(noteId, title, desc) {
    isUpdate = true;
    updateId = noteId;
    addBox.click();
    titleEl.value = title;
    descEl.value = desc;
    addBtn.innerText = 'Edit Note';
    popupTitle.innerText = 'Editing a Note';
}


addBox.addEventListener('click', ()=>{
    titleEl.focus();
    popupBox.classList.add('show')
});

closeIcon.addEventListener('click', ()=>{
    isUpdate = false;
    titleEl.value = '';
    descEl.value = '';
    addBtn.innerText = 'Add Note';
    popupTitle.innerText = 'Add a new Note';
    popupBox.classList.remove('show');
});

addBtn.addEventListener('click', (e)=>{
    e.preventDefault();
    let noteTitle = titleEl.value,
    noteDesc = descEl.value;
    if (noteTitle || noteDesc) {
        let dateEl= new Date(),
        month = months[dateEl.getMonth()],
        day = dateEl.getDate(),
        year = dateEl.getFullYear();


        let noteInfo = {
            title: noteTitle,
            description: noteDesc,
            date: `${month} ${day} ${year}`
        }

        if (!isUpdate) {
            notes.push(noteInfo);
        }else{
            isUpdate = false;
            notes[updateId] = noteInfo;
        }

        localStorage.setItem('notes', JSON.stringify(notes));
        closeIcon.click();
        showNotes();
    }
});

这是实现 HTML 和 CSS 后的样子：

接着，我们再来看一下JavaScript 的示例代码：

const addBox = document.querySelector('.add-box'),
popupBox = document.querySelector('.popup-box'),
popupTitle = popupBox.querySelector('header p'),
closeIcon = document.querySelector('header i'),
titleEl = document.querySelector('input'),
descEl = document.querySelector('textarea'),
addBtn = document.querySelector('button ');


const months= ['January', 'Febuary', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']

const notes = JSON.parse(localStorage.getItem('notes') || '[]');
let isUpdate = false, updateId;

function showNotes() {
    document.querySelectorAll('.note').forEach(note => note.remove());
    notes.forEach((note, index)=>{
        let liEl=`<li class="note">
                        <div class="details">
                            <p>${note.title}</p>
                            <span>${note.description}</span>
                        </div>
                        <div class="bottom-content">
                            <span>${note.date}</span>
                            <div class="settings">
                                <i onClick="updateNote(${index}, '${note.title}', '${note.description}')"  class="uil uil-edit"></i>
                                <i onClick="deleteNote(${index})" class="uil uil-trash"></i>
                            </div>
                        </div>
                    </li>`;
        addBox.insertAdjacentHTML('afterend', liEl);
    });
}

showNotes();

function deleteNote(noteId) {
    let confirmDelete= confirm("Are you sure you want to delete this note?");
    if(!confirmDelete) return;
    notes.splice(noteId, 1);
    localStorage.setItem('notes', JSON.stringify(notes));
    showNotes();
}

function updateNote(noteId, title, desc) {
    isUpdate = true;
    updateId = noteId;
    addBox.click();
    titleEl.value = title;
    descEl.value = desc;
    addBtn.innerText = 'Edit Note';
    popupTitle.innerText = 'Editing a Note';
}


addBox.addEventListener('click', ()=>{
    titleEl.focus();
    popupBox.classList.add('show')
});

closeIcon.addEventListener('click', ()=>{
    isUpdate = false;
    titleEl.value = '';
    descEl.value = '';
    addBtn.innerText = 'Add Note';
    popupTitle.innerText = 'Add a new Note';
    popupBox.classList.remove('show');
});

addBtn.addEventListener('click', (e)=>{
    e.preventDefault();
    let noteTitle = titleEl.value,
    noteDesc = descEl.value;
    if (noteTitle || noteDesc) {
        let dateEl= new Date(),
        month = months[dateEl.getMonth()],
        day = dateEl.getDate(),
        year = dateEl.getFullYear();


        let noteInfo = {
            title: noteTitle,
            description: noteDesc,
            date: `${month} ${day} ${year}`
        }

        if (!isUpdate) {
            notes.push(noteInfo);
        }else{
            isUpdate = false;
            notes[updateId] = noteInfo;
        }

        localStorage.setItem('notes', JSON.stringify(notes));
        closeIcon.click();
        showNotes();
    }
});

最后，这是添加 JavaScript 后的样子：

注意：您可以通过单击添加注释图标添加新注释，通过单击编辑图标编辑注释并通过单击垃圾桶图标删除注释。

例如，添加新笔记：

编辑笔记：

所有笔记都将存储在 Web 浏览器的本地存储中，因此刷新页面后仍会显示笔记。

到这里，这个实现案例就完成了，恭喜，你做到了！你已经会构建一个笔记应用程序。