Summary of methods for calling json from js

This article mainly gives you a detailed analysis of the summary of js calling json method. Friends in need can refer to it and learn from it. I hope it can help everyone.

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 users 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 transferred 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, the security is relatively high, and there is no cache

Preparing native Ajax

Ajax operation steps

Create 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 cache method:

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

Synchronization: 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 synchronous

Send request

Ajax.send();

Receive return value

Request status monitoring: onreadystatechange event: When between your own Ajax and the server Triggered when there is communication. It is mainly judged by the readyState attribute. The end does not mean success. The status attribute is used to judge the

readyState attribute: the request status

0 (not initialized) is not yet available. Calling the open method

1(Loading)The send() method has been called and the request is being sent

2(Loading completed)The send() method has been completed and all corresponding content has been received

3 (Parsing) The received response content is being parsed

4 (Complete) The response content parsing is completed and can be called on the client (completion does not necessarily mean success, status is required to detect success or failure) )

status attribute:

Request result, whether successful (200) or failed (404): Ajax.status==200

Return value responseText:

Text returned from the server: Ajax.responseText (the returned value is a string, sometimes it 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);
    }
  }
}

Convert native Ajax Encapsulate it 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, such as both utf8

Cache, prevent caching (frequently changing data, etc., cannot be cached. Mainly used for GET method), when passing parameters, add ?+'variable data' after the path to 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, which can be read and returned after conversion by eval Array/json data

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

2 Combined with DOM to create elements 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>&#39;+arr[i].user+&#39;</span>密码:<span>&#39;+arr[i].pass+&#39;</span>&#39;;
      oUl.appendChild(oLi);
    }
  },function(str){
    alert(str);
  });
}

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

Let’s take a look at an example where I just recently wrote native js and called 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;
    }
  }
}

Related recommendations:

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After PHP5.5 installation json_encode cannot be called. Solution

Instructions for using ajax to call json data in jquery_jquery

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