学习用JavaScript对数据进行CRUD操作
一、什么是 CRUD
CRUD就是我们常说的对数据的 增，查，改，删 操作
- C: Create
- R: Read
- U: Update
- D: Delete
二、 CRUD 程序的基本逻辑
三、留言板小程序-01
页面内有效，关闭或刷新页面后数据会消失
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| <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>留言板</title>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.1.1/css/all.min.css">
</head>
<body>
<div>
<h1>留言板</h1>
<label for="postInput">添加一个留言 </label>
<input type="text" id="postInput" value="" />
<button id="insertBtn" onclick="insertPost()">提交</button>
<span id="msgSpan" style="color:red;"></span>
</div>
<hr>
<div>
<ul id="postUl">
</ul>
</div>
</body>
<script type="text/javascript">
let postInput = document.getElementById("postInput")
let postUl = document.getElementById("postUl")
let msgSpan = document.getElementById("msgSpan")
let postId = 0;
let insertPost = () => {
if (postInput.value === "") {
msgSpan.innerText = "留言不能为空"
return false
}
postId++
postUl.innerHTML += `
<li id=${postId} >${postInput.value}
<i class="fa-solid fa-edit" title="修改" onclick=editPost(${postId})></i>
<i class="fa-solid fa-trash-can" title="删除" onclick=delPost(${postId})></i>
</li>
`
postInput.value = ""
msgSpan.innerText = ""
}
let editPost = (id) => {
let postLi = document.getElementById(id)
postInput.value = postLi.innerText.trim()
postLi.remove()
}
let delPost = (id) => {
let postLi = document.getElementById(id)
postLi.remove()
}
</script>
</html>
|
四、留言板小程序-02
将数据保存在浏览器数据库（LocalStorage）中，关闭或刷新页面后数据不会消失
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| <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>留言板（localstorage）</title>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.1.1/css/all.min.css">
</head>
<body>
<div>
<h1>留言板（localstorage）</h1>
<label for="postInput">添加一个留言 </label>
<input type="text" id="postInput" value="" />
<button id="insertBtn" onclick="insertPost()">提交</button>
<span id="msgSpan" style="color:red;"></span>
</div>
<hr>
<div>
<ul id="postUl">
</ul>
</div>
</body>
<script type="text/javascript">
let postInput = document.getElementById("postInput")
let postUl = document.getElementById("postUl")
let msgSpan = document.getElementById("msgSpan")
let postArray = []
let insertPost = () => {
if (postInput.value === "") {
msgSpan.innerText = "留言不能为空"
return false
}
let postId = Math.random().toString(36).substring(7)
postArray.push({
"post_id": postId,
"post_val": postInput.value
})
localStorage.setItem("posts", JSON.stringify(postArray))
postInput.value = ""
msgSpan.innerText = ""
showPosts()
}
let editPost = (id) => {
postArray.forEach((post) => {
if (post.post_id === id) {
postInput.value = post.post_val
}
})
delPost(id)
}
let delPost = (id) => {
postArray = postArray.filter((post) => {
return post.post_id != id
})
localStorage.setItem("posts", JSON.stringify(postArray))
showPosts()
}
let showPosts = () => {
postUl.innerHTML = ""
let posts = localStorage.getItem("posts")
if (posts != null) {
postArray = JSON.parse(posts)
postArray.forEach((post) => {
postUl.innerHTML += `
<li>${post.post_val}
<i class="fa-solid fa-edit" title="修改" onclick=editPost("${post.post_id}")></i>
<i class="fa-solid fa-trash-can" title="删除" onclick=delPost("${post.post_id}")></i>
</li>
`
})
}
}
showPosts()
</script>
</html>
|
浏览器中的显示结果
