Make a deep copy of the given data set.

morris.coffee

@@ -21,6 +21,10 @@ class Morris.Line
     # bail if there's no data
     if @options.data is undefined or @options.data.length is 0
       return
+    else
+       # otherwise create a deep copy of the input data: we'll perform
+       # operations on it later so better not taint the user's data.
+       @options.data = clone(@options.data)
     @el.addClass 'graph-initialised'
     @precalc()
     @redraw()
@@ -514,6 +518,31 @@ Morris.labelSeries = (dmin, dmax, pxwidth, specName, xLabelFormat) ->
     spec.incr(d)
   return ret
 
+# Perform a deep copy of the given object.
+# Source: http://coffeescriptcookbook.com/chapters/classes_and_objects/cloning
+clone = (obj) ->
+  if not obj? or typeof obj isnt 'object'
+    return obj
+
+  if obj instanceof Date
+    return new Date(obj.getTime())
+
+  if obj instanceof RegExp
+    flags = ''
+    flags += 'g' if obj.global?
+    flags += 'i' if obj.ignoreCase?
+    flags += 'm' if obj.multiline?
+    flags += 'y' if obj.sticky?
+    return new RegExp(obj.source, flags)
+
+  newInstance = new obj.constructor()
+
+  for key of obj
+    newInstance[key] = clone obj[key]
+
+  return newInstance
+
+
 minutesSpecHelper = (interval) ->
   span: interval * 60 * 1000
   start: (d) -> new Date(d.getFullYear(), d.getMonth(), d.getDate(), d.getHours())

morris.js

@@ -1,6 +1,6 @@
 // Generated by CoffeeScript 1.3.1
 (function() {
-  var $, Morris, minutesSpecHelper, secondsSpecHelper,
+  var $, Morris, clone, minutesSpecHelper, secondsSpecHelper,
     __bind = function(fn, me){ return function(){ return fn.apply(me, arguments); }; };
 
   $ = jQuery;
@@ -35,6 +35,8 @@
       }
       if (this.options.data === void 0 || this.options.data.length === 0) {
         return;
+      } else {
+        this.options.data = clone(this.options.data);
       }
       this.el.addClass('graph-initialised');
       this.precalc();
@@ -586,6 +588,37 @@
     return ret;
   };
 
+  clone = function(obj) {
+    var flags, key, newInstance;
+    if (!(obj != null) || typeof obj !== 'object') {
+      return obj;
+    }
+    if (obj instanceof Date) {
+      return new Date(obj.getTime());
+    }
+    if (obj instanceof RegExp) {
+      flags = '';
+      if (obj.global != null) {
+        flags += 'g';
+      }
+      if (obj.ignoreCase != null) {
+        flags += 'i';
+      }
+      if (obj.multiline != null) {
+        flags += 'm';
+      }
+      if (obj.sticky != null) {
+        flags += 'y';
+      }
+      return new RegExp(obj.source, flags);
+    }
+    newInstance = new obj.constructor();
+    for (key in obj) {
+      newInstance[key] = clone(obj[key]);
+    }
+    return newInstance;
+  };
+
   minutesSpecHelper = function(interval) {
     return {
       span: interval * 60 * 1000,

test/test.html

@@ -3,6 +3,7 @@
   <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
   <link rel="stylesheet" href="http://code.jquery.com/qunit/git/qunit.css" type="text/css" media="screen" />
   <script type="text/javascript" src="http://code.jquery.com/qunit/git/qunit.js"></script>
+  <script type="text/javascript" src="http://github.com/DmitryBaranovskiy/raphael/raw/master/raphael-min.js"></script>
   <script type="text/javascript" src="../morris.js"></script>
 
   <script>
@@ -10,6 +11,19 @@
 
     module("Morris");
 
+    test("Input data remains untouched", function() {
+        var my_data = [{x: 1, y: 1}, {x: 2, y: 2}];
+        var expected_data = [{x: 1, y: 1}, {x: 2, y: 2}];
+        Morris.Line({
+            element: "graph-placeholder",
+            data: my_data,
+            xkey: 'x',
+            ykeys: ['y'],
+            labels: ['dontcare']
+        });
+        deepEqual(my_data, expected_data);
+    });
+
     test("Morris.commas", function () {
       // zero
       equal(Morris.commas(0), "0", "commas(0) = 0")
@@ -215,6 +229,8 @@
   <div id="qunit-testrunner-toolbar"></div>
   <h2 id="qunit-userAgent"></h2>
   <ol id="qunit-tests"></ol>
-  <div id="qunit-fixture">test markup, will be hidden</div>
+  <div id="qunit-fixture">
+      <div id="graph-placeholder" style="width: 100px; height: 50px"></div>
+  </div>
 </body>
 </html>