Native javascript implements parsing XML documents and strings_javascript skills

I previously wrote an article "How to use jquery to parse XML". The link is http://www.jb51.net/article/54842.htm. The previous article explained jQuery and strings in detail The method of mutual conversion, here focuses on the operation of javascript xml.

The total code is as follows:

var XMLHttp = null;
if (window.XMLHttpRequest) { //现代浏览器
  XMLHttp = new XMLHttpRequest();
} else if (window.ActiveXObject) {
  XMLHttp = new ActiveXObject("Microsoft.XMLHTTP"); //IE5/IE6
}
if (XMLHttp !== null) {
  XMLHttp.onreadystatechange = function() {
    if (XMLHttp.readyState === 4) {
      if (XMLHttp.status === 200 || XMLHttp.status === 304) {
        // var XMLDom = XMLHttp.responseXML; //解析XML文档
        var XMLDoc = XMLHttp.responseText; //解析XML字符串
        var XMLDom = (new DOMParser()).parseFromString(XMLDoc, "text/xml");
        //异步代码写这里
        console.log(XMLDom);
        console.log("world"); //后出现world
      }
    }
  };
  XMLHttp.open("get", "test1.xml", true);
  XMLHttp.send();
  //非异步代码写这里
  console.log("hello"); //先出现hello
}

The first step is to create XMLHTTPREQUEST:

var XMLHttp = null;
if (window.XMLHttpRequest) { //现代浏览器
  XMLHttp = new XMLHttpRequest();
} else if (window.ActiveXObject) {
  XMLHttp = new ActiveXObject("Microsoft.XMLHTTP"); //IE5/IE6
}

The second step is to detect ONREADYSTATECHANGE (not required for non-asynchronous):

if (XMLHttp !== null) {
  XMLHttp.onreadystatechange = function() {
    if (XMLHttp.readyState === 4) {
      if (XMLHttp.status === 200 || XMLHttp.status === 304) {
        //异步代码写这里
      }
    }
  };
  XMLHttp.open("get", "test1.xml", true);
  XMLHttp.send();
  //非异步代码写这里
}

The third step, parse XML document or string (asynchronous):

XMLHttp.onreadystatechange = function() {
    if (XMLHttp.readyState === 4) {
      if (XMLHttp.status === 200 || XMLHttp.status === 304) {
        // var XMLDom = XMLHttp.responseXML; //解析XML文档
        var XMLDoc = XMLHttp.responseText; //解析XML字符串
        var XMLDom = (new DOMParser()).parseFromString(XMLDoc, "text/xml");
        //异步代码写这里
        console.log(XMLDom);
      }
    }
  };
  

The fourth step, parse XML document or string (non-asynchronous):

if (XMLHttp !== null) {
  // XMLHttp.onreadystatechange = function() {
  //   if (XMLHttp.readyState === 4) {
  //     if (XMLHttp.status === 200 || XMLHttp.status === 304) {}
  //   }
  // };
  XMLHttp.open("get", "test1.xml", false);
  XMLHttp.send();
  //非异步代码写这里
  // var XMLDom = XMLHttp.responseXML; //解析XML文档
  var XMLDoc = XMLHttp.responseText; //解析XML字符串
  var XMLDom = (new DOMParser()).parseFromString(XMLDoc, "text/xml");
  //异步代码写这里
  console.log(XMLDom);
}