Challenge 19 & 20 Added

Author: sahilatahar

README.md

@@ -154,22 +154,38 @@ Write a function called `celsiusToFahrenheit` that takes a temperature in Celsiu
 
 [Solution Explanation](./solutions/ch_16_Celsius_To_Fahrenheit/readme.md)
 
-## Challenge 17: Calculate the Sum of N Natural Number.
+## Challenge 17: Calculate the Sum of N Natural Number
 
 Write a function that takes a number as input and returns sum from 1 to `n`. For example, if the input is 10, the function should return 55.
 
 Write a function called `getNaturalSum` that takes a number `n` as its parameter and returns sum of natural number.
 
 [Solution Explanation](./solutions/ch_17_Sum_Of_N_Natural_Number/readme.md)
 
-## Challenge 18: Convert Decimal to Binary.
+## Challenge 18: Convert Decimal to Binary
 
 Write a function that takes a decimal number as input and returns binary string. For example, if the input is 12, the function should return 1100.
 
 Write a function called `decimalToBinary` that takes a decimal number as `decimal` in its parameter and returns binary string.
 
 [Solution Explanation](./solutions/ch_18_Decimal_To_Binary/readme.md)
 
+## Challenge 19: Count Vowels in a String
+
+Write a function that takes a string as input and returns number of vowels in string. For example, if the string is "Hello World!", the function should return 3.
+
+Write a function called `countVowels` that takes a string as `str` in its parameter and returns number of vowels in string.
+
+[Solution Explanation](./solutions/ch_19_Count_Vowels_In_String/readme.md)
+
+## Challenge 20: Check String Url
+
+Write a function that takes a url string as input and returns true if url is valid and false otherwise. For example, if the string is "https://www.example.com", the function should return true.
+
+Write a function called `isValidURL` that takes a string url as `url` in its parameter and returns true or false.
+
+[Solution Explanation](./solutions/ch_20_Check_String_Url/readme.md)
+
 <!-- Add new challenges before this comment -->
 
 ## Contributors

solutions/ch_19_Count_Vowels_In_String/answer.js

@@ -0,0 +1,17 @@
+// Function to count vowels in the string
+function countVowels(str) {
+
+    str = str.toLowerCase(); // Convert string to lower case
+
+    const vowels = ['a', 'e', 'i', 'o', 'u']; // List of vowels
+    let count = 0; // Declare variable to count number of vowels
+
+    for (let i = 0; i < str.length; i++) {
+        // Checking if vowels include the character at str[i]
+        if (vowels.includes(str[i])) {
+            count++;
+        }
+    }
+
+    return count; // Return the total number of vowels
+}

solutions/ch_19_Count_Vowels_In_String/readme.md

@@ -0,0 +1,31 @@
+# Challenge 19: Count Vowels in a String
+
+Write a function that takes a string as input and returns number of vowels in string. For example, if the string is "Hello World!", the function should return 3.
+
+Write a function called `countVowels` that takes a string as `str` in its parameter and returns number of vowels in string.
+
+## Answer
+
+```javascript
+// Function to count vowels in the string
+function countVowels(str) {
+
+    str = str.toLowerCase(); // Convert string to lower case
+
+    const vowels = ['a', 'e', 'i', 'o', 'u']; // List of vowels
+    let count = 0; // Declare variable to count number of vowels
+
+    for (let i = 0; i < str.length; i++) {
+        // Checking if vowels include the character at str[i]
+        if (vowels.includes(str[i])) {
+            count++;
+        }
+    }
+
+    return count; // Return the total number of vowels
+}
+```
+
+## Answer Explanation
+
+In the `countVowels` function, first convert `str` string to lowercase. Declare `count` variable to store number of vowels in `str` and declare `vowels` array of vowels and run a loop for every character in `str`. Inside the loop check if str[index] contains vowels character if yes increase count variable by one. After the loop finished return `count`, total number of vowels.

solutions/ch_20_Check_String_Url/answer.js

@@ -0,0 +1,8 @@
+// Function to check string url
+function isValidURL(url) {
+    // Regular expression pattern for URL validation
+    const urlPattern = /^(https?:\/\/)?[\w\-]+(\.[\w\-]+)+[/#?]?.*$/i;
+
+    // Test if the string matches the URL pattern
+    return urlPattern.test(url);
+}

solutions/ch_20_Check_String_Url/readme.md

@@ -0,0 +1,24 @@
+# Challenge 20: Check String Url
+
+Write a function that takes a url string as input and returns true if url is valid and false otherwise. For example, if the string is "https://www.example.com", the function should return true.
+
+Write a function called `isValidURL` that takes a string url as `url` in its parameter and returns true or false.
+
+## Answer
+
+```javascript
+// Function to check string url
+function isValidURL(url) {
+  // Regular expression pattern for URL validation
+  const urlPattern = /^(https?:\/\/)?[\w\-]+(\.[\w\-]+)+[/#?]?.*$/i;
+
+  // Test if the string matches the URL pattern
+  return urlPattern.test(url);
+}
+```
+
+## Answer Explanation
+
+The `isValidURL` function takes a string as input and uses a regular expression to check if it's a valid URL. The regular expression `^(https?:\/\/)?[\w\-]+(\.[\w\-]+)+[/#?]?.*$` is used to match the URL pattern.
+
+The test method is then used to check if the input string matches the regular expression, if it's a valid URL function returns true otherwise false.