锚(Anchor)是什么?
之前我是这样认为的:锚是一个href="#id"或者“#name”这种a标签,主要用于页面内元素的快速定位,实现书签或者目录的功能。
后来我改变了对锚的看法,才识庐山真面目。
现在我对它的有了全新的认识:锚是一个anchor标签,即标签。锚通过href属性可以链接到其它页面,也可以链接到当前页面的某个位置。
我们平时常说的锚点,或者锚链接,其实都是锚,叫法虽然不同但是本质一样,就像“西红柿”和“番茄”一样,只是一种叫法。网上对锚点或者锚链接的解释也是五花八门,存在有歧义的问题最好去官方网站上寻求答案,比如MDN或者W3C(FQ版,中文版更新的慢,而且不一定准确)寻找答案。
锚在MDN上是这样描述的“
我英语不好,但是还是能读懂这句话的意思。这里就不作翻译了,怕出丑。
页面上每一个标签都会为其创建一个Anchor对象,当然我们也可以通过document.createElement("A")去创建一个锚,关于Anchor对象的详细介绍请访问HTML DOM Anchor Object。
我们可以通过document.anchors[] 数组来获取锚,也可以使用 document.getElementById()或者其它获取dom对象的方法。
注意:document.anchors[]只能获取带有name属性的锚,如果锚没有name属性,可以通过document.getElementById()访问。
hash
大概意思就是url#号后面(包含#)的片段,这个片段不是被压缩过得(后面这句我也不知道怎么翻译........)。
hash是一个可读可写的属性,有两种方式可以取得hash,window.location.hash或者用window.location.href然后通过第一个#进行截取
hash的可以用来跨域,通过iframe加上location.hash组合方式实现js跨域,还可以利用hashchange实现ajax前进后退或者单页面试图切换,比如Angular路由
onhashchange
MDN这样介绍的:
当url#号后的字符包括#号发生改变时会触发onhashchange事件。
那么怎么才会改变#号后的内容呢?
主要有四种方式:
1、手动改变浏览器地址栏的url的hash值,即修改url#号后面的部分
2、通过代码改变hash值,如window.location.href = "url#hash",或者window.location.hash = "yourhash"。
3、通过锚改变hash值,href="#号+id"或者href="#号+name"。
4、通过浏览器自带的前进和后退也有可能触发onhashchange,因为hash改变虽然没有进行页面reload,但是会将hash改变后的url写入历史中,比如点击一个锚链接,页面滚动到某个位置,此时url的hash值已经改变,点击后退按钮会触发hashchange。
举栗,利用hash原理实现ajax前进后退功能
我们都知道ajax请求不会在浏览器中产生历史记录,如果想看前一个请求的数据,按浏览器的后退键是没有用的,只有重新填写查询条件,然后再执行查询才能得到想要的结果。这样在有些场景下是不合理的。利用hashchange解决上面的的问题,举栗子:
ajax请求是58同城里的搜索框的数据,输入苹果->搜索,输入橙子->搜索,点击后退按钮回到苹果列表页面。
下面是一种实现方式。感兴趣的可以亲自试一下。
<span style="color: #0000ff;"><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">html</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">head</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">meta </span><span style="color: #ff0000;">http-equiv</span><span style="color: #0000ff;">="Content-Type"</span><span style="color: #ff0000;"> content</span><span style="color: #0000ff;">="text/html; charset=utf-8"</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>hashchange<span style="color: #0000ff;"></span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">style</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;"> p</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;"> font-size</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 24px</span><span style="background-color: #f5f5f5; color: #000000;">;</span> <span style="background-color: #f5f5f5; color: #000000;">}</span> <span style="color: #0000ff;"></span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"></span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">script </span><span style="color: #ff0000;">type</span><span style="color: #0000ff;">="text/javascript"</span><span style="color: #ff0000;"> src </span><span style="color: #0000ff;">= "jquery.js"</span><span style="color: #0000ff;">></span><span style="color: #800000;">script</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">script </span><span style="color: #ff0000;">type </span><span style="color: #0000ff;">= "text/javascript"</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #000000;"> $(</span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;">(){ $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">button</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).click(</span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;">(){ </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> queryText </span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;"> $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#search</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).val(); query(queryText); }) }); </span><span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">注册hashchange事件,为了兼容低版本IE,用了两种方式进行注册</span> <span style="background-color: #f5f5f5; color: #000000;"> window.addEventListener(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">hashchange</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">,hashCallBack); window.attachEvent(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">onhashchange</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">,hashCallBack); </span><span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">hash改变的监听函数</span> <span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;"> hashCallBack(e){ </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> queryText </span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;"> window.location.hash.split(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">)[</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">]; </span><span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">获取hash值</span> <span style="background-color: #f5f5f5; color: #0000ff;">if</span><span style="background-color: #f5f5f5; color: #000000;">(queryText </span><span style="background-color: #f5f5f5; color: #000000;">==</span><span style="background-color: #f5f5f5; color: #000000;"> $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#search</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).val()) </span><span style="background-color: #f5f5f5; color: #0000ff;">return</span> <span style="background-color: #f5f5f5; color: #0000ff;">if</span><span style="background-color: #f5f5f5; color: #000000;">(queryText){ $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#search</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).val(queryText); }</span><span style="background-color: #f5f5f5; color: #0000ff;">else</span><span style="background-color: #f5f5f5; color: #000000;">{ $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#search</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).val(</span><span style="background-color: #f5f5f5; color: #000000;">""</span><span style="background-color: #f5f5f5; color: #000000;">); } query(queryText); } </span><span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">查询按钮</span> <span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;"> query(queryText){ $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#content</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).empty(); $.ajax({ url:</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">http://suggest.58.com.cn/searchsuggest_14.do?inputbox=</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">+</span><span style="background-color: #f5f5f5; color: #000000;">queryText</span><span style="background-color: #f5f5f5; color: #000000;">+</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">&cityid=1&catid=0&callback=callback1538</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">, type:</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">get</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">, dataType:</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">jsonP</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">, success:</span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;">(e){ console.log(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">成功</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">); } }); } </span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;"> callback1538(data){ window.location.hash </span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;"> $(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">#search</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).val(); </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> arr </span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;"> data.w; </span><span style="background-color: #f5f5f5; color: #0000ff;">for</span><span style="background-color: #f5f5f5; color: #000000;">( </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> i </span><span style="background-color: #f5f5f5; color: #000000;">=</span> <span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">;i</span><span style="background-color: #f5f5f5; color: #000000;"><span style="background-color: #f5f5f5; color: #000000;">arr.length;i</span><span style="background-color: #f5f5f5; color: #000000;">++</span><span style="background-color: #f5f5f5; color: #000000;">){ </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> p </span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;"> document.createElement(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">p</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">); </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> textnode</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">document.createTextNode(arr[i].k); p.appendChild(textnode); document.getElementById(</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">content</span><span style="background-color: #f5f5f5; color: #000000;">"</span><span style="background-color: #f5f5f5; color: #000000;">).appendChild(p); } } </span><span style="color: #0000ff;"></span><span style="color: #800000;">script</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">body</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">input </span><span style="color: #ff0000;">type </span><span style="color: #0000ff;">= "text"</span><span style="color: #ff0000;"> id </span><span style="color: #0000ff;">= "search"</span><span style="color: #0000ff;">><span style="color: #800000;">button</span><span style="color: #0000ff;">></span>搜索<span style="color: #0000ff;"></span><span style="color: #800000;">button</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">id </span><span style="color: #0000ff;">= "content"</span><span style="color: #0000ff;">></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"></span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span> <span style="color: #0000ff;"></span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
本章内容就完稿了,内容虽然不多,但是却花费了很大的精力,总之收获还是多多的。
其实我这篇文章就阐述了一个观点,锚不仅仅是定位而已。
如果你觉得我哪里说的不正确,还望指正。

The future trends of HTML are semantics and web components, the future trends of CSS are CSS-in-JS and CSSHoudini, and the future trends of JavaScript are WebAssembly and Serverless. 1. HTML semantics improve accessibility and SEO effects, and Web components improve development efficiency, but attention should be paid to browser compatibility. 2. CSS-in-JS enhances style management flexibility but may increase file size. CSSHoudini allows direct operation of CSS rendering. 3.WebAssembly optimizes browser application performance but has a steep learning curve, and Serverless simplifies development but requires optimization of cold start problems.

The roles of HTML, CSS and JavaScript in web development are: 1. HTML defines the web page structure, 2. CSS controls the web page style, and 3. JavaScript adds dynamic behavior. Together, they build the framework, aesthetics and interactivity of modern websites.

The future of HTML is full of infinite possibilities. 1) New features and standards will include more semantic tags and the popularity of WebComponents. 2) The web design trend will continue to develop towards responsive and accessible design. 3) Performance optimization will improve the user experience through responsive image loading and lazy loading technologies.

The roles of HTML, CSS and JavaScript in web development are: HTML is responsible for content structure, CSS is responsible for style, and JavaScript is responsible for dynamic behavior. 1. HTML defines the web page structure and content through tags to ensure semantics. 2. CSS controls the web page style through selectors and attributes to make it beautiful and easy to read. 3. JavaScript controls web page behavior through scripts to achieve dynamic and interactive functions.

HTMLisnotaprogramminglanguage;itisamarkuplanguage.1)HTMLstructuresandformatswebcontentusingtags.2)ItworkswithCSSforstylingandJavaScriptforinteractivity,enhancingwebdevelopment.

HTML is the cornerstone of building web page structure. 1. HTML defines the content structure and semantics, and uses, etc. tags. 2. Provide semantic markers, such as, etc., to improve SEO effect. 3. To realize user interaction through tags, pay attention to form verification. 4. Use advanced elements such as, combined with JavaScript to achieve dynamic effects. 5. Common errors include unclosed labels and unquoted attribute values, and verification tools are required. 6. Optimization strategies include reducing HTTP requests, compressing HTML, using semantic tags, etc.

HTML is a language used to build web pages, defining web page structure and content through tags and attributes. 1) HTML organizes document structure through tags, such as,. 2) The browser parses HTML to build the DOM and renders the web page. 3) New features of HTML5, such as, enhance multimedia functions. 4) Common errors include unclosed labels and unquoted attribute values. 5) Optimization suggestions include using semantic tags and reducing file size.

WebdevelopmentreliesonHTML,CSS,andJavaScript:1)HTMLstructurescontent,2)CSSstylesit,and3)JavaScriptaddsinteractivity,formingthebasisofmodernwebexperiences.


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