How to call json in native js
This time I will show you how to call json from native js. What are the precautions for calling json from native js? Here are practical cases, let’s take a look.
Ajax basics
ajax: No refresh data reading, reading information on the serverHTTP request method:
GET: used to obtain data, such as browsing postsajax.judgeXmlHttpRequest('get', 'index.php', function(data){ alert(data); //这是服务器返回的数据 })
var dataJson = { name: 'ys',age: 123 } ajax.judgeXmlHttpRequest('post', 'index.php', function(data){ alert(data); //这是服务器返回的数据 },dataJson)
The difference between GET and POST:
GET: Passed through the URL (put into the URL), the passed data will be placed on the URL, name = Value & name = valueThe get method has small capacity, low security, and cachePOST: does not pass through the URLThe post capacity is large, generally up to 2G, Relatively high security, no cachingNative Ajax writingAjax running steps
Creating an Ajax objectNon IE6 browser:var oAjax=new XMLHttpRequest();
var oAjax=new ActiveXObject("Microsoft.XMLHTTP");
Connect to the server
Ajax.open(方法,文件名,异步传输);
Ajax.open('GET','a.txt?t='+new Date().getTime(),true);
Ajax.send();
Receive return value
Request status monitoring: onreadystatechange event: Triggered when there is communication between your own Ajax and the server, mainly through the readyState attribute to determine whether it has ended. , the end does not mean success, the status attribute is used to judge the readyState attribute: the request status 0 (not initialized) has not called the open method 1 (loading ) The send() method has been called and the request is being sent 2 (Loading completed) The send() method is completed and all corresponding content has been received 3 (Analysis) The received message is being parsed Response content 4 (Complete) The response content parsing is completed and can be called on the client (completion is not necessarily successful, status is required to detect success or failure) status attribute:Request result, whether it is success (200) or failure (404): Ajax.status==200Return value responseText:Text returned from the server: Ajax.responseText( The returned value is a string, which sometimes needs to be further processed into other formats)
oAjax.onreadystatechange=function(){ //oAjax.readyState: 表示浏览器和服务器之间进行到哪一步了 if(oAjax.readyState==4){ //读取完成 if(oAjax.status==200){ //读取的结果是成功 alert('成功:'+oAjax.responseText); } } }
The function encapsulated by the GET method is:
function ajax(url,fnSuccess,fnFaild){ //1.创建Ajax对象。js中,使用一个没有定义的变量会报错,使用一个没有定义的属性,是undefined。IE6下使用没有定义的XMLHttpRequest会报错,所以当做window的一个属性使用 if (window.XMLHttpRequest) { var oAjax=new XMLHttpRequest();//非IE6 }else{ var oAjax=new ActiveXObject("Microsoft.XMLHTTP");//IE6 } //2.连接到服务器 oAjax.open('GET',url,true); //3.发送请求 oAjax.send(); //4.接收返回值 oAjax.onreadystatechange=function(){ //oAjax.readyState--浏览器和服务器之间进行到哪一步了 if(oAjax.readyState==4){ //读取完成 if(oAjax.status==200){ //读取的结果是成功 fnSuccess(oAjax.responseText); //成功时执行的函数 }else{ if(fnFaild){ //判断是否传入失败是的函数,即用户是否关心失败时的结果 fnFaild(oAjax.responseText); //对失败的原因做出处理 } } } } }
The function encapsulated by the POST method is:
function ajaxPost(url,id,fnSuccess,fnFaild){ //1.创建Ajax对象 if (window.XMLHttpRequest) { var xhr=new XMLHttpRequest();//非IE6 }else{ var xhr=new ActiveXObject("Microsoft.XMLHTTP");//IE6 } //2.连接到服务器 xhr.open("POST",url,true); //设置头信息 xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded"); var form=document.getElementById(id); //3.发送请求,传递数据 xhr.send(serialize(form)); xhr.onreadystatechange=function(){ if(xhr.readyState==4){ if ((xhr.status>=200 && xhr.status<300) || xhr.status==304) { fnSuccess(xhr.responseText); }else{ fnFaild(xhr.responseText); } } }; }
ajax('a.txt?t='+new Date().getTime(),function(str){ alert(str); },function(str){ alert(str); });
ajax requests dynamic data: such as json file
1 The ajax return value is a string, and the returned array can be read through eval conversion /json dataalert(str); alert(typeof(str)); var arr=eval(str); alert(typeof(arr)); alert(arr[1]); alert(arr[1].c);
oBtn.onclick=function(){ ajax('data/arr3.txt?t='+new Date().getTime(),function(str){ var arr=eval(str); for (var i = 0; i < arr.length; i++) { var oLi=document.createElement('li'); oLi.innerHTML='用户名:<span>'+arr[i].user+'</span>密码:<span>'+arr[i].pass+'</span>'; oUl.appendChild(oLi); } },function(str){ alert(str); }); }
if(!isNaN(matchId)) { var xmlHttp = null; try {// Chrome, Firefox, Opera, Safari xmlHttp = new XMLHttpRequest(); }catch (e) { try {// Internet Explorer IE 6.0+ xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try {// Internet Explorer IE 5.5+ xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("your browser not support ajax!"); } } } window.onload = function () { xmlHttp.open("get",/api/clientMatch/commonMatchDiagram.json?matchId=" + matchId,true); xmlHttp.send(); xmlHttp.onreadystatechange = doResult; //设置回调函数 }; function doResult() { var html=''; if ((xmlHttp.readyState == 4)&&(xmlHttp.status == 200)) {//4代表执行完成,200代表执行成功 var data = JSON.parse(xmlHttp.responseText); if(data.code == 200){ //代码执行 } document.getElementById('appMatch').innerHTML = html; } } }
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