Added a simple tool to watch for changes in the source and automatically rebuild vis.js on changes

tools/watch.js

@@ -0,0 +1,33 @@
+/**
+ * Watch for changes in the sourcecode, and rebuild vis.js on change
+ *
+ * Usage:
+ *     cd vis
+ *     node tools/watch.js
+ */
+
+var watch = require('node-watch'),
+    child_process = require('child_process');
+
+// constants
+var WATCH_FOLDER = './src';
+var BUILD_COMMAND = 'jake build';
+
+// rebuilt vis.js on change of code
+function rebuild() {
+    var start = +new Date();
+    child_process.exec(BUILD_COMMAND, function () {
+        var end = +new Date();
+        console.log('rebuilt in ' + (end - start) + ' ms');
+    });
+}
+
+// watch for changes in the code, rebuilt vis.js automatically
+watch(WATCH_FOLDER, function(filename) {
+    console.log(filename, ' changed');
+    rebuild();
+});
+
+rebuild();
+
+console.log('watching for changes in the source code...');