JScript List and Property List

Question

Consider the following WSH snippet:

  var query = GetObject ("winmgmts:"). ExecQuery ("SELECT Name FROM Win32_Printer", "WQL", 0);
 var e = new Enumerator (query);
 for (;! e.atEnd (); e.moveNext ()) { 
     var p = e.item ();
     WScript.Echo (p.Name + "(" + p.Status + ")");
 }

It prints the name of the printer and the word "undefined" in brackets on each line (since the Status property does not exist in the p object). The question is: how can I list all available properties from p ? The usual method for (var i in p) {...} ...} does not work - it seems that the properties of the object p not listed.

Thanks in advance.

Answer 1

Operator

JScript for...in not compatible with WMI objects, because, moreover, they are more complex than native JScript objects. WMI objects expose their collection of properties using the special property Properties_ , so to list all the available properties of an object, you need to list this collection, for example, you list the results of a query to access individual WMI objects. Each property of an object is represented by a SWbemProperty object, which has a Name , Value and other properties that provide information about the corresponding object.

This example will help you understand:

 var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer"); var colPrinters = new Enumerator(query); var oPrinter, colProps, p; // Enumerate WMI objects for ( ; !colPrinters.atEnd(); colPrinters.moveNext()) { oPrinter = colPrinters.item(); // Enumerate WMI object properties colProps = new Enumerator(oPrinter.Properties_); for ( ; !colProps.atEnd(); colProps.moveNext()) { p = colProps.item(); WScript.Echo(p.Name + ": " + p.Value); } } ") ExecQuery ( "SELECT Name, Status FROM Win32_Printer");. var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer"); var colPrinters = new Enumerator(query); var oPrinter, colProps, p; // Enumerate WMI objects for ( ; !colPrinters.atEnd(); colPrinters.moveNext()) { oPrinter = colPrinters.item(); // Enumerate WMI object properties colProps = new Enumerator(oPrinter.Properties_); for ( ; !colProps.atEnd(); colProps.moveNext()) { p = colProps.item(); WScript.Echo(p.Name + ": " + p.Value); } } colPrinters.moveNext ()) { var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer"); var colPrinters = new Enumerator(query); var oPrinter, colProps, p; // Enumerate WMI objects for ( ; !colPrinters.atEnd(); colPrinters.moveNext()) { oPrinter = colPrinters.item(); // Enumerate WMI object properties colProps = new Enumerator(oPrinter.Properties_); for ( ; !colProps.atEnd(); colProps.moveNext()) { p = colProps.item(); WScript.Echo(p.Name + ": " + p.Value); } } colProps.moveNext ()) { var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer"); var colPrinters = new Enumerator(query); var oPrinter, colProps, p; // Enumerate WMI objects for ( ; !colPrinters.atEnd(); colPrinters.moveNext()) { oPrinter = colPrinters.item(); // Enumerate WMI object properties colProps = new Enumerator(oPrinter.Properties_); for ( ; !colProps.atEnd(); colProps.moveNext()) { p = colProps.item(); WScript.Echo(p.Name + ": " + p.Value); } } 

Note that this script also displays the value of the DeviceID property, because it is a key property of the Win32_Printer class, so it is also retrieved to uniquely identify instances of the class.

Answer 2

If you want to avoid having to use explicit Enumerator every time you need to sort through a collection object that he needs, you can define a little helper function as follows:

 function forEach(collection, func) { for (var e = new Enumerator(collection); !e.atEnd(); e.moveNext()) { func(e.item()); } } 

Collection iteration is becoming less awkward:

 var queryResult = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer"); // Enumerate WMI objects forEach (queryResult, function (oPrinter) { // Enumerate WMI object properties forEach (oPrinter.Properties_, function (p) { WScript.Echo(p.Name + ": " + p.Value); }); }); p.Value); var queryResult = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer"); // Enumerate WMI objects forEach (queryResult, function (oPrinter) { // Enumerate WMI object properties forEach (oPrinter.Properties_, function (p) { WScript.Echo(p.Name + ": " + p.Value); }); }); 

Answer 3

I think the problem is in your request, you are only asking for a name. Try to indicate the name and status:

 var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer", "WQL", 0); var e = new Enumerator(query); for ( ; !e.atEnd(); e.moveNext ()) { var p = e.item(); WScript.Echo(p.Name + " (" + p.Status + ")" ); } p.Status + ")"); var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status FROM Win32_Printer", "WQL", 0); var e = new Enumerator(query); for ( ; !e.atEnd(); e.moveNext ()) { var p = e.item(); WScript.Echo(p.Name + " (" + p.Status + ")" ); } 

I got some more properties from http://msdn.microsoft.com/en-us/library/aa394363(VS.85).aspx and a few works. I asked for DriverName and Comment, and both had a text or even zero.

 var query = GetObject("winmgmts:").ExecQuery("SELECT Name, Status, DriverName, Comment FROM Win32_Printer", "WQL", 0); var e = new Enumerator(query); for ( ; !e.atEnd(); e.moveNext ()) { var p = e.item(); WScript.Echo(p.Name + " (" + p.Status + ") " + p.DriverName + " " + p.Comment); }