Strapping down of Extend-routines in util.js (almende#3442)

* The next fix on Travis unit test failure

This is the next escalation on the war against the Travis unit tests failing (which came into being by yours truly).
By accident, I could recreate the unit test failure on my development machine. This led to a more directed effort to
squash the bug.

The insight here is that test `(window === undefined)` fails, but `(typeof window === 'undefined`)` succeeds. This undoubtedly has to do with the special status `window` has as a global object.

Changes:

- Added check on presence of `window` in `Canvas._requestNextFrame()`, fixed local source errors.
- Added catch clause in `CanvasRendered._determinePixelRatio()`
- small fix: raised timeout for the network `worldCup2014` unit test

* Preliminary refactoring in utils.js

* Added unit tests for extend routines, commenting and small fixes

* More unit tests for extend routines

* - Completed unit tests for extend routines in
- Small fixes and cleanup in `util.js`
- Removed `util.protoExtend()`, not used anywhere

* Added unit tests for known font options

lib/util.js

@@ -107,24 +107,49 @@ exports.assignAllKeys = function (obj, value) {
 
 
 /**
- * Fill an object with a possibly partially defined other object. Only copies values if the a object has an object requiring values.
+ * Copy property from b to a if property present in a.
+ * If property in b explicitly set to null, delete it if `allowDeletion` set.
+ *
+ * Internal helper routine, should not be exported. Not added to `exports` for that reason.
+ *
+ * @param {object} a  target object
+ * @param {object} b  source object
+ * @param {string} prop  name of property to copy to a
+ * @param {boolean} allowDeletion  if true, delete property in a if explicitly set to null in b 
+ * @private
+ */
+function copyOrDelete(a, b, prop, allowDeletion) {
+  var doDeletion = false;
+  if (allowDeletion === true) {
+    doDeletion = (b[prop] === null && a[prop] !== undefined);
+  }
+
+  if (doDeletion) {
+      delete a[prop];
+  } else {
+    a[prop] = b[prop];  // Remember, this is a reference copy!
+  }
+}
+
+
+/**
+ * Fill an object with a possibly partially defined other object.
+ *
+ * Only copies values for the properties already present in a.
  * That means an object is not created on a property if only the b object has it.
+ *
  * @param {object} a
  * @param {object} b
- * @param {boolean} [allowDeletion=false]
+ * @param {boolean} [allowDeletion=false]  if true, delete properties in a that are explicitly set to null in b 
  */
 exports.fillIfDefined = function (a, b, allowDeletion = false) {
+  // NOTE: iteration of properties of a
+  // NOTE: prototype properties iterated over as well
   for (var prop in a) {
     if (b[prop] !== undefined) {
-      if (typeof b[prop] !== 'object') {
-        if ((b[prop] === undefined || b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-          delete a[prop];
-        }
-        else {
-          a[prop] = b[prop];
-        }
-      }
-      else {
+      if (b[prop] === null || typeof b[prop] !== 'object') { // Note: typeof null === 'object'
+        copyOrDelete(a, b, prop, allowDeletion);
+      } else {
         if (typeof a[prop] === 'object') {
           exports.fillIfDefined(a[prop], b[prop], allowDeletion);
         }
@@ -134,24 +159,6 @@ exports.fillIfDefined = function (a, b, allowDeletion = false) {
 };
 
 
-
-/**
- * Extend object a with the properties of object b or a series of objects
- * Only properties with defined values are copied
- * @param {Object} a
- * @param {...Object} b
- * @return {Object} a
- */
-exports.protoExtend = function (a, b) {  // eslint-disable-line no-unused-vars
-  for (var i = 1; i < arguments.length; i++) {
-    var other = arguments[i];
-    for (var prop in other) {
-      a[prop] = other[prop];
-    }
-  }
-  return a;
-};
-
 /**
  * Extend object a with the properties of object b or a series of objects
  * Only properties with defined values are copied
@@ -197,153 +204,138 @@ exports.selectiveExtend = function (props, a, b) {  // eslint-disable-line no-un
   return a;
 };
 
+
 /**
- * Extend object a with selected properties of object b or a series of objects
- * Only properties with defined values are copied
- * @param {Array.<string>} props
- * @param {Object} a
- * @param {Object} b
- * @param {boolean} [allowDeletion=false]
- * @return {Object} a
+ * Extend object a with selected properties of object b.
+ * Only properties with defined values are copied.
+ *
+ * **Note:** Previous version of this routine implied that multiple source objects
+ *           could be used; however, the implementation was **wrong**.
+ *           Since multiple (>1) sources weren't used anywhere in the `vis.js` code,
+ *           this has been removed
+ *
+ * @param {Array.<string>} props names of first-level properties to copy over
+ * @param {object} a  target object
+ * @param {object} b  source object
+ * @param {boolean} [allowDeletion=false]  if true, delete property in a if explicitly set to null in b 
+ * @returns {Object} a
  */
 exports.selectiveDeepExtend = function (props, a, b, allowDeletion = false) {
   // TODO: add support for Arrays to deepExtend
   if (Array.isArray(b)) {
     throw new TypeError('Arrays are not supported by deepExtend');
   }
-  for (var i = 2; i < arguments.length; i++) {
-    var other = arguments[i];
-    for (var p = 0; p < props.length; p++) {
-      var prop = props[p];
-      if (other.hasOwnProperty(prop)) {
-        if (b[prop] && b[prop].constructor === Object) {
-          if (a[prop] === undefined) {
-            a[prop] = {};
-          }
-          if (a[prop].constructor === Object) {
-            exports.deepExtend(a[prop], b[prop], false, allowDeletion);
-          }
-          else {
-            if ((b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-              delete a[prop];
-            }
-            else {
-              a[prop] = b[prop];
-            }
-          }
-        } else if (Array.isArray(b[prop])) {
-          throw new TypeError('Arrays are not supported by deepExtend');
-        } else {
-          if ((b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-            delete a[prop];
-          }
-          else {
-            a[prop] = b[prop];
-          }
-        }
 
+  for (var p = 0; p < props.length; p++) {
+    var prop = props[p];
+    if (b.hasOwnProperty(prop)) {
+      if (b[prop] && b[prop].constructor === Object) {
+        if (a[prop] === undefined) {
+          a[prop] = {};
+        }
+        if (a[prop].constructor === Object) {
+          exports.deepExtend(a[prop], b[prop], false, allowDeletion);
+        }
+        else {
+          copyOrDelete(a, b, prop, allowDeletion);
+        }
+      } else if (Array.isArray(b[prop])) {
+        throw new TypeError('Arrays are not supported by deepExtend');
+      } else {
+        copyOrDelete(a, b, prop, allowDeletion);
       }
     }
   }
   return a;
 };
 
+
 /**
- * Extend object a with selected properties of object b or a series of objects
+ * Extend object `a` with properties of object `b`, ignoring properties which are explicitly specified
+ * to be excluded.
+ * 
+ * The properties of `b` are considered for copying.
+ * Properties which are themselves objects are are also extended.
  * Only properties with defined values are copied
- * @param {Array.<string>} props
- * @param {Object} a
- * @param {Object} b
- * @param {boolean} [allowDeletion=false]
+ *
+ * @param {Array.<string>} propsToExclude  names of properties which should *not* be copied
+ * @param {Object}                      a  object to extend
+ * @param {Object}                      b  object to take properties from for extension
+ * @param {boolean} [allowDeletion=false]  if true, delete properties in a that are explicitly set to null in b 
  * @return {Object} a
  */
-exports.selectiveNotDeepExtend = function (props, a, b, allowDeletion = false) {
+exports.selectiveNotDeepExtend = function (propsToExclude, a, b, allowDeletion = false) {
   // TODO: add support for Arrays to deepExtend
+  // NOTE: array properties have an else-below; apparently, there is a problem here. 
   if (Array.isArray(b)) {
     throw new TypeError('Arrays are not supported by deepExtend');
   }
+
   for (var prop in b) {
-    if (b.hasOwnProperty(prop)) {
-      if (props.indexOf(prop) == -1) {
-        if (b[prop] && b[prop].constructor === Object) {
-          if (a[prop] === undefined) {
-            a[prop] = {};
-          }
-          if (a[prop].constructor === Object) {
-            exports.deepExtend(a[prop], b[prop]);
-          }
-          else {
-            if ((b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-              delete a[prop];
-            }
-            else {
-              a[prop] = b[prop];
-            }
-          }
-        } else if (Array.isArray(b[prop])) {
-          a[prop] = [];
-          for (let i = 0; i < b[prop].length; i++) {
-            a[prop].push(b[prop][i]);
-          }
-        } else {
-          if ((b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-            delete a[prop];
-          }
-          else {
-            a[prop] = b[prop];
-          }
-        }
+    if (!b.hasOwnProperty(prop)) continue;              // Handle local properties only 
+    if (propsToExclude.indexOf(prop) !== -1) continue;  // In exclusion list, skip
+
+    if (b[prop] && b[prop].constructor === Object) {
+      if (a[prop] === undefined) {
+        a[prop] = {};
+      }
+      if (a[prop].constructor === Object) {
+        exports.deepExtend(a[prop], b[prop]);  // NOTE: allowDeletion not propagated!
+      }
+      else {
+        copyOrDelete(a, b, prop, allowDeletion);
+      }
+    } else if (Array.isArray(b[prop])) {
+      a[prop] = [];
+      for (let i = 0; i < b[prop].length; i++) {
+        a[prop].push(b[prop][i]);
       }
+    } else {
+      copyOrDelete(a, b, prop, allowDeletion);
     }
   }
+
   return a;
 };
 
+
 /**
  * Deep extend an object a with the properties of object b
+ *
  * @param {Object} a
  * @param {Object} b
- * @param {boolean} [protoExtend]   --> optional parameter. If true, the prototype values will also be extended.
- *                                    (ie. the options objects that inherit from others will also get the inherited options)
- * @param {boolean} [allowDeletion] --> optional parameter. If true, the values of fields that are null will be deleted
+ * @param {boolean} [protoExtend=false]  If true, the prototype values will also be extended.
+ *                          (ie. the options objects that inherit from others will also get the inherited options)
+ * @param {boolean} [allowDeletion=false] If true, the values of fields that are null will be deleted
  * @returns {Object}
  */
-exports.deepExtend = function (a, b, protoExtend, allowDeletion) {
+exports.deepExtend = function (a, b, protoExtend=false, allowDeletion=false) {
   for (var prop in b) {
     if (b.hasOwnProperty(prop) || protoExtend === true) {
       if (b[prop] && b[prop].constructor === Object) {
         if (a[prop] === undefined) {
           a[prop] = {};
         }
         if (a[prop].constructor === Object) {
-          exports.deepExtend(a[prop], b[prop], protoExtend);
+          exports.deepExtend(a[prop], b[prop], protoExtend);  // NOTE: allowDeletion not propagated!
         }
         else {
-          if ((b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-            delete a[prop];
-          }
-          else {
-            a[prop] = b[prop];
-          }
+          copyOrDelete(a, b, prop, allowDeletion);
         }
       } else if (Array.isArray(b[prop])) {
         a[prop] = [];
         for (let i = 0; i < b[prop].length; i++) {
           a[prop].push(b[prop][i]);
         }
       } else {
-        if ((b[prop] === null) && a[prop] !== undefined && allowDeletion === true) {
-          delete a[prop];
-        }
-        else {
-          a[prop] = b[prop];
-        }
+        copyOrDelete(a, b, prop, allowDeletion);
       }
     }
   }
   return a;
 };
 
+
 /**
  * Test whether all elements in two arrays are equal.
  * @param {Array} a