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 server

HTTP request method:

GET: used to obtain data, such as browsing posts

ajax.judgeXmlHttpRequest('get', 'index.php', function(data){
  alert(data);  //这是服务器返回的数据
})

POST: used to upload data, such as

user registration

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 = value

The get method has small capacity, low security, and cache

POST: does not pass through the URL

The post capacity is large, generally up to 2G, Relatively high security, no caching

Native Ajax writing

Ajax running steps

Creating an Ajax object

Non IE6 browser:

var oAjax=new XMLHttpRequest();

IE6 browser:

var oAjax=new ActiveXObject("Microsoft.XMLHTTP");

Connect to the server

Ajax.open(方法,文件名,异步传输);

Block caching method:

Ajax.open('GET','a.txt?t='+new Date().getTime(),true);

Sync :js means that things must be done one by one

Asynchronous:js means that multiple things must be done together

ajax is used for asynchronous transmission, not synchronously

Send requests

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==200

Return 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);
    }
  }
}

Encapsulate native Ajax into a function and use it. The final native Ajax written is:

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);
      }
    }
  };
}

Character set encoding: The encoding of the web page and the requested file must be The same, if they are all utf8

cache, to prevent caching (frequently changing data, etc., cannot be cached. Mainly used for GET method), when passing parameters, add ? + 'variable data' after the path. OK Does not affect the original data

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 data

alert(str);
alert(typeof(str));
var arr=eval(str);
alert(typeof(arr));
alert(arr[1]);
alert(arr[1].c);

2 Create elements combined with DOM to display the returned content

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(&#39;li&#39;);
      oLi.innerHTML=&#39;用户名:<span>'+arr[i].user+'</span>密码:<span>'+arr[i].pass+'</span>';
      oUl.appendChild(oLi);
    }
  },function(str){
    alert(str);
  });
}

Data type-->The returned data type may be xml (almost eliminated), json (now Commonly used)

Let’s take a look at an example where I recently wrote native js to call json through the get method:

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;
    }
  }
}

I believe you have mastered the method after reading the case in this article. For more exciting things, please pay attention to php Other related articles on the Chinese website!

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