recursion programs added and readme updated

Author: sanjaydeveloper15

README.md

@@ -41,3 +41,10 @@ When we have **String** or **Array** which creating a WINDOW from one position t
 ### Divide and Conquer Pattern
 
 It is related to our search and sorting algorithms, such as in Binery Search we divide the array from mid then search the element.
+
+### Recursion
+
+Keeps calling same function until didn't get expected result. Here few Points are so important otherwise our Call Stack will be infinite and size exceeding error comes:
+
+- Identify base case such as if (statement) return x;
+- It basically depends upon call stack, you can check call stack example in Examples directory.

Recursion/arithmetic-operations.js

@@ -0,0 +1,33 @@
+console.log('~~~~~~~ Sum ~~~~~~~~');
+
+const sumRange = (uptoNum) => {
+    console.log('uptoNum',uptoNum);
+    if(uptoNum === 1) return 1;
+    return uptoNum + sumRange(uptoNum -1);
+}
+
+console.log(sumRange(2));
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log(sumRange(3));
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log(sumRange(4));
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log(sumRange(5));
+
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log('~~~~~~~ Factorial ~~~~~~~~');
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+
+const factorial = (uptoNum) => {
+    console.log('uptoNum',uptoNum);
+    if(uptoNum === 1) return 1;
+    return uptoNum * factorial(uptoNum -1);
+}
+
+console.log(factorial(2));
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log(factorial(3));
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log(factorial(4));
+console.log('~~~~~~~~~~~~~~~~~~~~~')
+console.log(factorial(5));

Recursion/multidimensional-operations.js

@@ -0,0 +1,30 @@
+// Write a function called power which accepts a base and an exponent. 
+// The function should return the power of the base to the exponent. 
+// This function should mimic the functionality of Math.pow()  - do not worry about negative bases and exponents.
+console.log(`------- Question:1 --------`);
+const power = (base, exp) => {
+    console.log(base, exp)
+    if(exp === 0) return 1;
+    if(exp === 1) return base * 1;
+    return base * power(base, exp - 1);
+}
+
+console.log(power(2,0)) // 1
+console.log('----------------')
+console.log(power(2,2)) // 4
+console.log('----------------')
+console.log(power(2,4)) // 16
+console.log('----------------')
+
+// Write a function called productOfArray which takes in an array of numbers and returns the product of them all.
+console.log(`------- Question:2 --------`);
+const productOfArray = (inputArr) => {
+    let result = 1;
+    for(let i=0;i<inputArr.length; i++) {
+        result *= inputArr[i]
+    }
+    return result;
+}
+
+console.log(productOfArray([1,2,3])) // 6
+console.log(productOfArray([1,2,3,10])) // 60