Merge branch 'rachleona-master'

USER:rachleona added deepcompare algorithm on Repository.

Author: tejas-2232

README.md

@@ -562,15 +562,107 @@ Note that we chain both .replace() methods in succession such that both cases ar
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-<b>7. Name </b>
+<b>7. Deep Comparison </b>
 
-__The challenge:__ <p> </p>
+Comparing objects can be troublesome, not to mention multi-dimensional objects/arrays. Here is something simple to help.
 
+__The challenge:__ <p> - JS Objects, contrary to the way we perceive it, are simply pointers to the data stored, rather than the actual data itself. Thus, to compare objects/arrays a and b we cannot just use normal comparison operators.</p> 
+```js 
+a === b //false
+```
+<p> - Use of multidimensional objects/arrays is possible, making it difficult to compare simply by iteration since we don't know the depth of a value. </p>
+
+<p> - Different data types like Dates and undefined must also be taken into consideration. <p>
+ 
+ <p>Given the above, return a boolean signifying whether a and b are equivalent in content. </p>
+
+__Algorithmic Thinking:__ <p>As we would be comparing each item contained in the objects, a loop may be the first instinct to solving it. However, with the potential of multidimensional iterables, we would have to disect nested arrays in the same way when we encounter them. A combination of iteration and recursion is therefore necessary. So for each item of the array a data type check is necessary as well, to allow execution of a relevant comparison.
+ 
+ Breaking it down:
+ * check if ```a === b```
+ * check if ```a``` and ```b``` are both iterable
+ * iterate over ```a``` using keys and call deepCompare recursively
+</p>
 
-__Algorithmic Thinking:__ <p> </p>
 
+__code Implementation:__ <p> 
 
-__code Implementation:__ <p> </p>
+Firstly, we'll do the most simple check of ```a === b``` to avoid unnecessary complexity. This will process all of the equal literal values for us.
+
+```js 
+if(a === b) return true
+```
+
+Then comes the interesting part! There are several data types we need to look out for: Objects, Arrays(which JS treats as an object), and Dates(which is also treated as an object!), thus all we have to do is check if both a and b are of type object. If not, we can just return false as they didn't pass the ```a === b``` test.
+
+```js 
+if(typeof a === "object" && typeof b === "object")...
+```
+
+Note that we use ```===``` here to differentiate between data types strictly.
+
+Next, we can process the dates first, as that doesn't require iteration. Make sure to compare ```Date.valueOf()``` instead of the date object itself.
+
+```js 
+if(a instanceof Date && b instanceof Date) return a.valueOf() === b.valueOf() 
+```
+
+Lastly, by taking the keys of the iterables we can compare the length of ```a``` and ```b```, then make use of built-in Array.some method to check if any values of the two iterables don't match.
+
+```js
+//get keys/index of object/array a
+const keysA = Object.keys(a)
+
+//make sure a and b are the same length
+if(keysA.length !== Object.keys(b).length) return false
+   
+//Array.some() iterates through the values in an array and stops executing nested code until there is one that returns true
+//in this case that would be when there is one different value between a and b
+return !keysA.some( key => { 
+  //run deepCompare recursively
+  return !deepCompare(a[key], b[key])
+})
+ ```
+
+
+Put it all together, and we have
+
+```js
+const deepCompare = (a, b) => {
+  if(a === b) return true
+
+  if(typeof a === "object" && typeof b === "object")
+  {
+    if(a instanceof Date && b instanceof Date) return a.valueOf() === b.valueOf()
+    else 
+    {
+      const keysA = Object.keys(a)
+      if(keysA.length !== Object.keys(b).length) return false
+      return !keysA.some( key => {
+        return !deepCompare(a[key], b[key])
+      })
+    }
+  }
+  else return false
+}
+
+deepCompare(1, 2) 
+//false
+
+deepCompare({"first": 1, "second": 2}, {"first": 1, "second": 2})
+//true
+
+deepCompare([1, "2", 3.0], [1, "2", 3])
+//false
+
+const arr = [1, 2, "3", [{4: "5", 6: 7}, 8.0, new Date(), undefined]]
+deepCompare(arr, [1, 2, "3", [{4: "5", 6: 7}, 8.0, new Date(), undefined]]) 
+//true
+
+  ```
+  
+It's that simple! Hope this helps.
+</p>
 <hr>
 <hr>
 

deepCompare_7/deepCompare.js

@@ -0,0 +1,19 @@
+//deep comparison of multi-dimensional arrays with recursion
+
+const deepCompare = (a, b) => {
+  if(a === b) return true
+    
+  if(typeof a === "object" && typeof b === "object")
+  {
+    if(a instanceof Date && b instanceof Date) return a.valueOf() === b.valueOf()
+    else 
+    {
+      const keysA = Object.keys(a)
+      if(keysA.length !== Object.keys(b).length) return false
+      return !keysA.some( key => {
+        return !deepCompare(a[key], b[key])
+      })
+    }
+  }
+  else return false
+}