Implement deepEquality.js

deepEquality/deepEquality.js

@@ -11,5 +11,68 @@
   * don't worry about handling cyclical object structures.
   *
   */
-var deepEquals = function(apple, orange){
+var deepEquals = function (apple, orange) {
+  var isAppleArray, isOrangeArray;
+  var appleLen, orangeLen;
+  var appleKeys, orangeKeys;
+  var comparison, i, prop;
+
+  if ( apple === orange ) return true;
+  if ( isPrimitive(apple) && isPrimitive(orange) ) return apple === orange; // true or false
+  if ( isPrimitive(apple) || isPrimitive(orange) ) return false;
+
+  /*
+   * At this point:
+   * 1) apple and orange are not identical objects
+   * 2) neither are primitives
+   * 3) both are objects
+  */
+
+  isAppleArray  = Array.isArray(apple);
+  isOrangeArray = Array.isArray(orange);
+
+  if ( isAppleArray && isOrangeArray ) {
+    // apple and orange are both arrays
+    appleLen  = apple.length;
+    orangeLen = orange.length;
+
+    // break out early if neither arrays are the same length
+    if ( appleLen !== orangeLen ) return false;
+
+    for (i = 0; i < appleLen; i += 1) {
+      comparison = deepEquals( apple[i], orange[i] );
+      if ( !comparison ) return false; // break out early if any comparison is not deeply equal
+    }
+    // reaching here implies that all items in both arrays are equal
+    return true;
+  } else if ( isAppleArray || isOrangeArray ) {
+    return false;
+  } else {
+    // apple and orange are both objects
+
+    appleKeys  = Object.keys( apple );
+    orangeKeys = Object.keys( orange );
+    if ( appleKeys.length !== orangeKeys.length ) return false;
+
+    for (prop in apple) {
+      // check if prop is in orangeKeys
+      if ( !orange[prop] ) {
+        return false;
+      } else {
+        comparison = deepEquals( apple[prop], orange[prop] );
+        if ( !comparison ) return false;
+      }
+    }
+    // reaching here implies that all the items in both objects are equal
+    return true;
+  }
 };
+
+var isPrimitive = function (obj) {
+  var type = typeof obj;
+  return type === 'string'  ||
+         type === 'number'  ||
+         type === 'boolean' ||
+         obj  === void 0    ||
+         obj  === null;
+};