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This time I will bring you a summary of the four methods of dynamically introducing js. What are the precautions for the four methods of dynamically introducing js? The following is a practical case, let's take a look.
index.html
<html> <head> <meta content="text/html;charset=utf-8" http-equiv="content-type"> <title> </title> <script src='' id="s1"></script> <script src="dynamic.js"></script> </head> <body> </body> </html>
test.js
alert("hello! I am test.js");
var str="1";
dynamic.js
//第一种方式：直接document.write 但这样会把当前的页面全覆写掉
//document.write("<script src='test.js'><\/script>");
//第二种方式:动态改变已有script的src属性
//s1.src="test.js"
//第三种方式：动态创建script元素
/* var oHead = document.getElementsByTagName('HEAD').item(0);
var oScript= document.createElement("script");
oScript.type = "text/javascript";
oScript.src="test.js";
oHead.appendChild(oScript);
*/
//其实原理就是利用dom动态的引入一个js到文件中来~就能和原有的js通信了~
//alert(str);
/*以上三种方式都采用异步加载机制，也就是加载过程中，页面会往下走，
如果这样的话会有问题的,如上面的str就访问不到，因为当程序执行alert(str)时，test.js还在加载Ing....
那么第四种就是基于ajax请求的,且是推荐
*/
function GetHttpRequest()
{
if ( window.XMLHttpRequest ) // Gecko
return new XMLHttpRequest() ;
else if ( window.ActiveXObject ) // IE
return new ActiveXObject("MsXml2.XmlHttp") ;
}
function ajaxPage(sId, url){
var oXmlHttp = GetHttpRequest() ;
oXmlHttp.onreadystatechange = function()
{
if (oXmlHttp.readyState == 4)
{
includeJS( sId, url, oXmlHttp.responseText );
}
}
oXmlHttp.open('GET', url, false);//同步操作
oXmlHttp.send(null);
}
function includeJS(sId, fileUrl, source)
{
if ( ( source != null ) && ( !document.getElementById( sId ) ) ){
var oHead = document.getElementsByTagName('HEAD').item(0);
var oScript = document.createElement( "script" );
oScript.type = "text/javascript";
oScript.id = sId;
oScript.text = source;
oHead.appendChild( oScript );
}
}
ajaxPage( "scrA", "test.js" );
alert( "主页面动态加载JS脚本。");
alert( "主页面动态加载a.js并取其中的变量：" + str ); I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website! Recommended reading:
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