Minor changes by Valera.

common/lib/xmodule/xmodule/js/src/capa/imageinput.js

-/////////////////////////////////////////////////////////////////////////////
-//
-//  Simple image input
-//
-////////////////////////////////////////////////////////////////////////////////
+/**
+ * Simple image input
+ *
+ *
+ * Click on image. Update the coordinates of a dot on the image.
+ * The new coordinates are the location of the click.
+ */
 
-// click on image, update coordinates
-// put a dot at location of click, on image
+/**
+ * 'The wise adapt themselves to circumstances, as water molds itself to the
+ * pitcher.'
+ *
+ * ~ Chinese Proverb
+ */
 
 window.image_input_click = function (id, event) {
-    var iidiv = document.getElementById("imageinput_" + id),
-        pos_x = event.offsetX ? (event.offsetX) : event.pageX - iidiv.offsetLeft,
-        pos_y = event.offsetY ? (event.offsetY) : event.pageY - iidiv.offsetTop,
+    var iiDiv = document.getElementById('imageinput_' + id),
+
+        posX = event.offsetX ? event.offsetX : event.pageX - iiDiv.offsetLeft,
+        posY = event.offsetY ? event.offsetY : event.pageY - iiDiv.offsetTop,
+
+        cross = document.getElementById('cross_' + id),
+
         // To reduce differences between values returned by different kinds of
-        // browsers, we round `pos_x` and `pos_y`.
-        // IE10: `pos_x` and `pos_y` - float.
-        // Chrome, FF: `pos_x` and `pos_y` - integers.
-        result = "[" + Math.round(pos_x) + "," + Math.round(pos_y) + "]",
-        cx = (pos_x - 15) + "px",
-        cy = (pos_y - 15) + "px",
-        cross = document.getElementById("cross_" + id);
+        // browsers, we round `posX` and `posY`.
+        //
+        // IE10: `posX` and `posY` - float.
+        // Chrome, FF: `posX` and `posY` - integers.
+        result = '[' + Math.round(posX) + ',' + Math.round(posY) + ']';
+
+    cross.style.left = (posX - 15) + 'px';
+    cross.style.top = (posY - 15) + 'px';
+    cross.style.visibility = 'visible';
 
-    cross.style.left = cx;
-    cross.style.top = cy;
-    cross.style.visibility = "visible" ;
-    document.getElementById("input_" + id).value = result;
+    document.getElementById('input_' + id).value = result;
 };