How to use native js to implement Ajax
This article mainly introduces how to use native js to implement Ajax. It has certain reference value. Now I share it with you. Friends in need can refer to it
Create Ajax Object
Connect to server
-
Send request
- `send()`接受一个参数(作为请求主体发送的数据),如果没有数据则必须传入`null`,因为这个参数对有些浏览器来说是必须的。调用`send()`之后,请求就会被分配到服务器
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Receive return
- 客户端和服务器端有交互的时候会调用`onreadystatechange` - oAjax.`readyState` **表示请求/响应过程的当前活动阶段**。 - 0->(未初始化):还没有调用 `open()` 方法。 - 1->(载入):已调用 `send()` 方法,正在发送请求。 - 2->载入完成):`send()` 方法完成,已收到全部响应内容。 - 3->(解析):正在解析响应内容。 - 4->(完成):响应内容解析完成,可以在客户端调用。 - `responseText`:作为响应主体被返回的文本; - `responseXML`:若响应的内容类型是`"text/xml"`或`"application/xml"`,该属性中将保存着包含着响应数据的`XML DOM`文档 - `status`:响应的`HTTP`状态; - `statusText`:`HTTP`状态的说明;
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/** * 原生js实现Ajax * @param url * @param fnSucc */ function ajax(url, fnSucc){ if(window.XMLHttpRequest){ var XHR = new XMLHTTPRequest(); }else{ var XHR = new ActiveXObject("Microsoft.XMLHTTP");//IE6浏览器创建ajax对象 } // readystate值每次改变,都会触发readystatechange事件 // 通常我们只对readstate值为4的阶段感兴趣 // 不过,必须在调用open()之前指定onreadystatechange事件处理程序,才能确保跨浏览器兼容性。 XHR.onreadystatechange = function(){ if(XHR.readyState == 4){ if(XHR.status >= 200 && XHR.status <= 300 || XHR.status == 304){ fnSucc(XHR.responseText);//成功的时候调用这个方法 }else{ if(fnFiled){ fnFiled(XHR.status); } } } } XHR.open("GET", url, true);//把要读取的参数的传过来, true:异步,false:同步 XHR.send(null);// send接受一个参数(作为请求主体发送的数据),如果没有数据则必须传入null,因为这个参数对有些浏览器来说是必须的。调用send()之后,请求就会被分配到服务器 }
/** * 支持更早期IE版本 IE5+ * @returns {XMLHttpRequest} */ function createXHR(){ if(typeof XMLHttpRequest != "undefined"){ return new XMLHttpRequest(); } else if(typeof ActiveXObject != "undefined"){ if(typeof arguments.callee.activeXString != "string"){ var versions = ["MSXML2.XMLHttp.6.0", "MSXML2.XMLHttp.3.0", "MSXML2.XMLHttp"], i, len = versions.length; for(i = 0; i < len; i++){ new ActiveXObject(versions[i]); arguments.callee.activeXString = versions[i]; berak; } } } else { throw new Error("No XHR object available.") } }
window.onload = function(){ var btn = document.getElementById("btn1"); btn.onclick = function(){ ajax('a.txt', function fnSucc(str){ alert(str) }); } }
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