平时做web开发的时候关于消息传递,除了客户端与服务器传值还有几个经常会遇到的问题1.页面和其打开的新窗口的数据传递2.多窗口之间消息传递3.页面与嵌套的iframe消息传递4.上面三个问题的跨域数据传递这些问题都有一些解决办法,但html5引入的message的API可以更方便、有效、安全的解决这些难题。postMessage()方法允许来自不同源的脚本采用异步方式进行有限的通信,可以实现跨文本档、多窗口、跨域消息传递。
postMessage(data,origin)方法接受两个参数
1.data:要传递的数据,html5规范中提到该参数可以是JavaScript的任意基本类型或可复制的对象,然而并不是所有浏览器都做到了这点儿,部分浏览器只能处理字符串参数,所以我们在传递参数的时候需要使用JSON.stringify()方法对对象参数序列化,在低版本IE中引用json2.js可以实现类似效果。
2.origin:字符串参数,指明目标窗口的源,协议+主机+端口号[+URL],URL会被忽略,所以可以不写,这个参数是为了安全考虑,postMessage()方法只会将message传递给指定窗口,当然如果愿意也可以建参数设置为"*",这样可以传递给任意窗口,如果要指定和当前窗口同源的话设置为"/"。
父页面
<!DOCTYPE html><html><head> <title>Post Message</title></head><body> <div style="width:200px; float:left; margin-right:200px;border:solid 1px #333;"> <div id="color">Frame Color</div> </div> <div> <iframe id="child" src="http://lsLib.com/lsLib.html"></iframe> </div> <script type="text/javascript"> window.onload=function(){ window.frames[0].postMessage('getcolor','http://lslib.com'); } window.addEventListener('message',function(e){ var color=e.data; document.getElementById('color').style.backgroundColor=color; },false); </script></body></html>
iframe页面
<!doctype html><html> <head> <style type="text/css"> html,body{ height:100%; margin:0px; } </style> </head> <body style="height:100%;"> <div id="container" onclick="changeColor();" style="widht:100%; height:100%; background-color:rgb(204, 102, 0);"> click to change color </div> <script type="text/javascript"> var container=document.getElementById('container'); window.addEventListener('message',function(e){ if(e.source!=window.parent) return; var color=container.style.backgroundColor; window.parent.postMessage(color,'*'); },false); function changeColor () { var color=container.style.backgroundColor; if(color=='rgb(204, 102, 0)'){ color='rgb(204, 204, 0)'; }else{ color='rgb(204,102,0)'; } container.style.backgroundColor=color; window.parent.postMessage(color,'*'); } </script> </body></html>

The function of HTML is to define the structure and content of a web page, and its purpose is to provide a standardized way to display information. 1) HTML organizes various parts of the web page through tags and attributes, such as titles and paragraphs. 2) It supports the separation of content and performance and improves maintenance efficiency. 3) HTML is extensible, allowing custom tags to enhance SEO.

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.


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