added solution to 4-random.js

Author: Alex Jamshidi

Sprint-1/1-key-exercises/4-random.js

@@ -7,3 +7,45 @@ const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
 // Try breaking down the expression and using documentation to explain what it means
 // It will help to think about the order in which expressions are evaluated
 // Try logging the value of num and running the program several times to build an idea of what the program is doing
+
+
+console.log(num)
+
+// num returns a value of 60, running it again returns a value of 15, looking at the code I see a .random() function
+// I can make a hypothesis that this returns a random number of some kind, hence the inconsistent result
+
+// Let's find out...
+// Code in inner-most brackets is evaluated first
+// I would expect (maximum - minimum + 1) to be evaluated first (100 - 1 + 1) would equal 100
+
+console.log(maximum - minimum + 1)
+
+// the result was 100
+// this part of the code is then multiplied by Math.random()
+
+console.log(Math.random())
+
+// running this code many times, it appears Math.random() returns a random number between 0 and 1
+// checking documentation online, this is correct (actually between 0 and 0.99999999999)
+// therefore Math.random() * (maximum - minimum + 1) should return a random number between 1 and 100
+
+console.log(Math.random() * (maximum - minimum + 1))
+
+// It does, it returns it with many decimal places, the result of num didn't have any decimal places
+// The next part of the code that is run is Math.floor, let's see what this does
+
+const number = Math.random() * (maximum - minimum + 1)
+console.log(number)
+console.log(Math.floor(number))
+
+// because Math.random() creates a new random number every time it is run, I had to set the
+// result to a variable so I can use the same number in multiple functions
+// When number is 87.52, Math.floor is 87, when number is 70.02, math.floor is 70
+// The function Math.floor appears to be rounding down
+// Checking the documentation, this is true, it returns the largest integer <= the given number
+
+// Therefore Math.floor(Math.random() * (maximum - minimum + 1)) must give random numbers between 0 and 99
+// The final part is the addition of minimum (+1)
+
+// Therefore I can see this code produces a random whole integer between minimum and maximum
+// Which in this case is an integer between 1 and 100