Web Storage是HTML5引入的一个非常重要的功能,可以在客户端本地存储数据,类似HTML4的cookie,但可实现功能要比cookie强大的多,cookie大小被限制在4KB,Web Storage官方建议为每个网站5MB。
Web Storage又分为两种:
- sessionStorage
- localStorage
从字面意思就可以很清楚的看出来,sessionStorage将数据保存在session中,浏览器关闭也就没了;而localStorage则一直将数据保存在客户端本地;
不管是sessionStorage,还是localStorage,可使用的API都相同,常用的有如下几个(以localStorage为例):
- 保存数据:localStorage.setItem(key,value);
- 读取数据:localStorage.getItem(key);
- 删除单个数据:localStorage.removeItem(key);
- 删除所有数据:localStorage.clear();
- 得到某个索引的key:localStorage.key(index);
如上,key和value都必须为字符串,换言之,web Storage的API只能操作字符串。
接下来,我们通过Web Storage开发一个简单的通讯录小程序,以演示相关API的使用方法;我们要实现如下功能:
- 录入联系人,联系人有姓名、手机号码2个字段,以手机号作为key存入localStorage;
- 根据手机号码,查找机主;
- 列出当前已保存的所有联系人信息;
首先,准备一个简单的HTML页面,如下:
- nbsp;HTML>
- html>
- head>
- meta charset="utf-8"/>
- title>HTML5本地存储之Web Storage篇title>
- head>
- body>
- div style="border: 2px dashed #ccc;width:320px;text-align:center;">
- label for="user_name">姓名:label>
- input type="text" id="user_name" name="user_name" class="text"/>
- br/>
- label for="mobilephone">手机:label>
- input type="text" id="mobilephone" name="mobilephone"/>
- br/>
- input type="button" onclick="save()" value="新增记录"/>
- hr/>
- label for="search_phone">输入手机号:label>
- input type="text" id="search_phone" name="search_phone"/>
- input type="button" onclick="find()" value="查找机主"/>
- p id="find_result">br/>p>
- div>
- br/>
- div id="list">
- div>
- body>
- html>
<meta charset="utf-8"> <title>HTML5本地存储之Web Storage篇</title> <div style="border: 2px dashed #ccc;width:320px;text-align:center;"> <label for="user_name">姓名:</label> <input type="text" id="user_name" name="user_name" class="text"> <br> <label for="mobilephone">手机:</label> <input type="text" id="mobilephone" name="mobilephone"> <br> <input type="button" onclick="save()" value="新增记录"> <hr> <label for="search_phone">输入手机号:</label> <input type="text" id="search_phone" name="search_phone"> <input type="button" onclick="find()" value="查找机主"> <p id="find_result"><br></p> </div> <br> <div id="list"> </div>
要实现联系人的保存,只需要简单实现如下JS方法即可:
- //保存数据
- function save(){
- var mobilephone = document.getElementById("mobilephone").value;
- var user_name = document.getElementById("user_name").value;
- localStorage.setItem(mobilephone,user_name);
- }
//保存数据 function save(){ var mobilephone = document.getElementById("mobilephone").value; var user_name = document.getElementById("user_name").value; localStorage.setItem(mobilephone,user_name); }
- //查找数据
- function find(){
- var search_phone = document.getElementById("search_phone").value;
- var name = localStorage.getItem(search_phone);
- var find_result = document.getElementById("find_result");
- find_result.innerHTML = search_phone + "的机主是:" + name;
- }
//查找数据 function find(){ var search_phone = document.getElementById("search_phone").value; var name = localStorage.getItem(search_phone); var find_result = document.getElementById("find_result"); find_result.innerHTML = search_phone + "的机主是:" + name; }
要展现所有已保存的联系人信息,则需要使用localStorage.key(index)方法,如下:
- //将所有存储在localStorage中的对象提取出来,并展现到界面上
- function loadAll(){
- var list = document.getElementById("list");
- if(localStorage.length>0){
- var result = "
";
";- result += "
姓名 手机号码 - for(var i=0;i
- var mobilephone = localStorage.key(i);
- var name = localStorage.getItem(mobilephone);
- result += "
"+name+" "+mobilephone+" - }
- result += "
- result += "
- list.innerHTML = result;
- }else{
- list.innerHTML = "目前数据为空,赶紧开始加入联系人吧";
- }
- }
//将所有存储在localStorage中的对象提取出来,并展现到界面上 function loadAll(){ var list = document.getElementById("list"); if(localStorage.length>0){ var result = "
姓名 | 手机号码 | "+name+" | "+mobilephone+" | "; } result += "
如下简单演示增加了公司属性的联系人保存JS代码:
- //保存数据
- function save(){
- var contact = new Object;
- contact.user_name = document.getElementById("user_name").value;
- contact.mobilephone = document.getElementById("mobilephone").value;
- contact.company = document.getElementById("company").value;
- var str = JSON.stringify(contact);
- localStorage.setItem(contact.mobilephone,str);
- loadAll();
- }
- //将所有存储在localStorage中的对象提取出来,并展现到界面上
- function loadAll(){
- var list = document.getElementById("list");
- if(localStorage.length>0){
- var result = "
";
";- result += "
姓名 手机 公司 - for(var i=0;i
- var mobilephone = localStorage.key(i);
- var str = localStorage.getItem(mobilephone);
- var contact = JSON.parse(str);
- result += "
"+contact.user_name+" "+contact.mobilephone+" "+contact.company+" - }
- result += "
- result += "
- list.innerHTML = result;
- }else{
- list.innerHTML = "目前数据为空,赶紧开始加入联系人吧";
- }
- }
//保存数据 function save(){ var contact = new Object; contact.user_name = document.getElementById("user_name").value; contact.mobilephone = document.getElementById("mobilephone").value; contact.company = document.getElementById("company").value; var str = JSON.stringify(contact); localStorage.setItem(contact.mobilephone,str); loadAll(); } //将所有存储在localStorage中的对象提取出来,并展现到界面上 function loadAll(){ var list = document.getElementById("list"); if(localStorage.length>0){ var result = "
姓名 | 手机 | 公司 | "+contact.user_name+" | "+contact.mobilephone+" | "+contact.company+" | "; } result += "

HTML5 code consists of tags, elements and attributes: 1. The tag defines the content type and is surrounded by angle brackets, such as. 2. Elements are composed of start tags, contents and end tags, such as contents. 3. Attributes define key-value pairs in the start tag, enhance functions, such as. These are the basic units for building web structure.

HTML5 is a key technology for building modern web pages, providing many new elements and features. 1. HTML5 introduces semantic elements such as, , etc., which enhances web page structure and SEO. 2. Support multimedia elements and embed media without plug-ins. 3. Forms enhance new input types and verification properties, simplifying the verification process. 4. Offer offline and local storage functions to improve web page performance and user experience.

Best practices for H5 code include: 1. Use correct DOCTYPE declarations and character encoding; 2. Use semantic tags; 3. Reduce HTTP requests; 4. Use asynchronous loading; 5. Optimize images. These practices can improve the efficiency, maintainability and user experience of web pages.

Web standards and technologies have evolved from HTML4, CSS2 and simple JavaScript to date and have undergone significant developments. 1) HTML5 introduces APIs such as Canvas and WebStorage, which enhances the complexity and interactivity of web applications. 2) CSS3 adds animation and transition functions to make the page more effective. 3) JavaScript improves development efficiency and code readability through modern syntax of Node.js and ES6, such as arrow functions and classes. These changes have promoted the development of performance optimization and best practices of web applications.

H5 is not just the abbreviation of HTML5, it represents a wider modern web development technology ecosystem: 1. H5 includes HTML5, CSS3, JavaScript and related APIs and technologies; 2. It provides a richer, interactive and smooth user experience, and can run seamlessly on multiple devices; 3. Using the H5 technology stack, you can create responsive web pages and complex interactive functions.

H5 and HTML5 refer to the same thing, namely HTML5. HTML5 is the fifth version of HTML, bringing new features such as semantic tags, multimedia support, canvas and graphics, offline storage and local storage, improving the expressiveness and interactivity of web pages.

H5referstoHTML5,apivotaltechnologyinwebdevelopment.1)HTML5introducesnewelementsandAPIsforrich,dynamicwebapplications.2)Itsupportsmultimediawithoutplugins,enhancinguserexperienceacrossdevices.3)SemanticelementsimprovecontentstructureandSEO.4)H5'srespo

The tools and frameworks that need to be mastered in H5 development include Vue.js, React and Webpack. 1.Vue.js is suitable for building user interfaces and supports component development. 2.React optimizes page rendering through virtual DOM, suitable for complex applications. 3.Webpack is used for module packaging and optimize resource loading.


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