These two are pretty straight forward. Just a few lines of javascript to convert:

    this.jclass = function(name) {
      if (typeof(name) == "string") {
         var clazz = sapkg.utilities.SystemDictionaryHelper.findInstanceKlass(name);
         if (clazz) {
             writeln(clazz.getName().asString() + " @" + clazz.getAddress().toString());
         } else {
             writeln("class not found: " + name);
         }
      } else {
         writeln("Usage: class name");
      }
    }
    registerCommand("class", "class name", "jclass");

    this.jclasses = function() {
      forEachKlass(function (clazz) {
        writeln(clazz.getName().asString() + " @" + clazz.getAddress().toString());
      });
    }
    registerCommand("classes", "classes", "jclasses");

Logic for forEachKlass() already exists in SA and there are plenty of examples to leverage.