restored the deleted file

Author: Pretty Taruvinga

Sprint-3/4-stretch/README.md

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+# 🔍 Stretch
+
+These stretch activities are not mandatory, but we hope you will explore them after you have completed the mandatory work.
+
+In this exercise, you'll need to **play computer** with the function `find`. This function makes use of while loop statement. Your task will be to step through the code to figure out what is happening when the computer executes the code.
+
+Next, try implementing the functions specified in `password-validator.js`.
+
+Finally, set up your own script and test files for `card-validator.md`

Sprint-3/4-stretch/card-validator.md

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+## **PROJECT: Credit Card Validator**
+
+In this project you'll write a script that validates whether or not a credit card number is valid.
+
+Here are the rules for a valid number:
+
+- Number must be 16 digits, all of them must be numbers.
+- You must have at least two different digits represented (all of the digits cannot be the same).
+- The final digit must be even.
+- The sum of all the digits must be greater than 16.
+
+For example, the following credit card numbers are valid:
+
+```markdown
+9999777788880000
+6666666666661666
+```
+
+And the following credit card numbers are invalid:
+
+```markdown
+a92332119c011112 (invalid characters)
+4444444444444444 (only one type of number)
+1111111111111110 (sum less than 16)
+6666666666666661 (odd final number)
+```
+
+These are the requirements your project needs to fulfill:
+
+- Make a JavaScript file with a name that describes its contents.
+- Create a function with a descriptive name which makes it clear what the function does. The function should take one argument, the credit card number to validate.
+- Write at least 2 comments that explain to others what a line of code is meant to do.
+- Return a boolean from the function to indicate whether the credit card number is valid.
+
+Good luck!

Sprint-3/4-stretch/find.js

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+function find(str, char) {
+  let index = 0;
+
+  while (index < str.length) {
+    if (str[index] === char) {
+      return index;
+    }
+    index++;
+  }
+  return -1;
+}
+
+console.log(find("code your future", "u"));
+console.log(find("code your future", "z"));
+
+// The while loop statement allows us to do iteration - the repetition of a certain number of tasks according to some condition
+// See the docs https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/while
+
+// Use the Python Visualiser to help you play computer with this example and observe how this code is executed
+// Pay particular attention to the following:
+
+// a) How the index variable updates during the call to find
+// b) What is the if statement used to check
+// c) Why is index++ being used?
+// d) What is the condition index < str.length used for?

Sprint-3/4-stretch/password-validator.js

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+function passwordValidator(password) {
+    return password.length < 5 ? false : true
+}
+
+
+module.exports = passwordValidator;

Sprint-3/4-stretch/password-validator.test.js

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+/* 
+Password Validation
+
+Write a program that should check if a password is valid
+and returns a boolean
+
+To be valid, a password must:
+- Have at least 5 characters.
+- Have at least one English uppercase letter (A-Z)
+- Have at least one English lowercase letter (a-z)
+- Have at least one number (0-9)
+- Have at least one of the following non-alphanumeric symbols: ("!", "#", "$", "%", ".", "*", "&")
+- Must not be any previous password in the passwords array. 
+
+You must breakdown this problem in order to solve it. Find one test case first and get that working
+*/
+const isValidPassword = require("./password-validator");
+test("password has at least 5 characters", () => {
+    // Arrange
+    const password = "12345";
+    // Act
+    const result = isValidPassword(password);
+    // Assert
+    expect(result).toEqual(true);
+}
+);