Added support for property filtering to the JSON output

index.js

@@ -335,7 +335,12 @@ function onLoadDOM(dom) {
 			return;
 		}
 		if (outputJSON){
-			writeStream.write(JSON.stringify(article));
+			var result = {};
+			for (propkey in wantedProperties) {
+			    let prop = wantedProperties[propkey];
+			    result[prop] = article[prop];
+			}
+			writeStream.write(JSON.stringify(result));
 			return;
 		}