Provide example reading of TTree using TSelector class

linev · linev · commit 3e45171784c5 · 2017-02-23T14:03:02.000+01:00
diff --git a/demo/read_tree.htm b/demo/read_tree.htm
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+
+   <meta charset="UTF-8">
+   <meta http-equiv="X-UA-Compatible" content="IE=edge">
+
+   <title>Reading object from the ROOT file</title>
+
+   <script src="../scripts/JSRootCore.min.js" type="text/javascript"></script>
+
+   <script type='text/javascript'>
+     // absolute file path can be used as well
+     var filename = "../../files/hsimple.root";
+     JSROOT.OpenFile(filename, function(file) {
+        file.ReadObject("ntuple;1", function(tree) {
+              
+              var selector = new JSROOT.TSelector();
+              
+              selector.AddBranch("px"); 
+              selector.AddBranch("py");
+              
+              var cnt = 0, sumpx = 0, sumpy = 0;
+              
+              selector.Begin = function() {
+                 // function called before reading of TTree starts
+                 document.getElementById('p_start').innerHTML = "Start reading TTree";
+              }
+              
+              selector.Process = function() {
+                 // function called for every entry
+                 sumpx += this.tgtobj.px;
+                 sumpy += this.tgtobj.py;
+                 cnt++;
+                 document.getElementById('p_process').innerHTML = "Process " + cnt + " entries";
+              }
+              
+              selector.Terminate = function(res) {
+                 // function called when processing finishes
+                 if (!res || (cnt===0)) res = "Fail to process TTree";
+                                   else res = 'MeanPX = ' +  (sumpx/cnt).toFixed(4) + '  MeanPY = ' + (sumpy/cnt).toFixed(4);
+                 document.getElementById('p_ready').innerHTML = res;
+              }
+              
+              tree.Process(selector);
+        });
+     });
+   </script>
+
+</head>
+
+<body>
+  <p id="p_start">...</p>
+  <p id="p_process">...</p>
+  <p id="p_ready">...</p>
+</body>
+
+</html>
+
diff --git a/docs/api.htm b/docs/api.htm
@@ -173,6 +173,7 @@ <h1 id="version"><a href=".." style="color:green">JSROOT</a></h1>
               { name: "File hierarchy", url: "demo/file_hierarchy.htm", title: "Use HierarchyPainter to display file objects hiararchy", src: true },
               { name: "Zooming", url: "demo/zoom_handler.htm", title: "Redefine Zoom function to make synchronous zooming in other histogram", src: true },
               { name: "User IO", url: "index.htm?file=" + filepath + "amore.root&item=moH1F_0;1&load=demo/amore.js", title : "Example of custom streamer and custom draw function (AMORE)", src: "demo/amore.js" },
+              { name: "Read tree", url: "demo/read_tree.htm", title: "Read data from TTree using TSelector class", src: true },
               { name: "User tree", url: "index.htm?file=https://root.cern/files/markus.root&item=_Event;1/Refs&opt=dump&load=demo/gaudi.js", title : "Example of user custom streamer for reading TTree data (Gaudi)", src: "demo/gaudi.js" }
             ],
             'httpserver.C' : [
