Javascript-DomParser-如何确定非XML字符串

Question

Here is something I need to do:

1. Parse any given string, make sure it is in XML format.
2. Count the nodes number if it is XML format. And return true.
3. Return false if the string is non XML.

I was trying to use a DOMParser to do the job, however, regardless what string I give it to the DOMParser, it always treat it as XML, and count it has 6 nodes.

Here is my script:

function invoke(msg){
try{
    var parser = new DOMParser();
    var xmlDoc = parser.parseFromString(msg,"text/xml");
    var nodes = xmlDoc.getElementsByTagName('*')
    console.log('The string is: ' + msg);
    console.log('This string has ' + nodes.length + ' nodes.');
    return true;
 }

 catch(err){
     console.log('The string is: ' + msg);
     console.log('Cannot read this string');
     return false;
}
}

invoke("hello world");
invoke("▒0藤▒]Ir▒|̆x▒$۾▒e▒(E▒>Ӆ▒▒▒ܩ▒b▒b▒▒=▒▒\q▒▒▒▒▒1▒▒▒");
invoke("<music><album>Beethoven</album></music>");

And the following screenshot is the output of my test, and seems it counts the total nodes correctly if the string is XML:

Could anyone please help.

Cheers, Vincent

Answer 1

Check for parsererror in the xmlDoc.

function invoke(msg){
  try{
    var parser = new DOMParser();
    var xmlDoc = parser.parseFromString(msg,"text/xml");
    if( xmlDoc.getElementsByTagName('parsererror').length ) {
      console.log('The string is: ' + msg);
      console.log('Cannot read this string');
      return false;
    } else {
      var nodes = xmlDoc.getElementsByTagName('*');
      console.log('The string is: ' + msg);
      console.log('This string has ' + nodes.length + ' nodes.');
      return true;
    }
  }
  catch(err){
   console.log('The string is: ' + msg);
   console.log('Cannot read this string');
   return false;
  }
}