W2D2 Checkpoint.js

# W2D2 Checkpoint

// I'M HAVING THE HARDEST TIME WITH LOOPS (FOR, DO, WHILE "ALL OF THE ABOVE") AND INCORPORATING LOOPS INTO THE FUNCTIONS!!!' 
   

Submit a link to your gist [here](https://goo.gl/forms/HywFjkNIU9mLM7c03)

1. Write a function `average` that takes two numbers as input (parameters), and
   returns the average of those numbers.

   function average (num1, num2) {
    return ((num1 + num2) / 2)
   }

   average(2, 4); // 3

2. Write a function `greeter` that takes a name as an argument and *greets*
    that name by returning something along the lines of `"Hello, <name>!"`

    function greeter (name) {
      return "Hello, " + name + "!";
    }

    greeter("Alex");

    // "Hello, Alex!"

3. Write the following functions that each accept a single number as an
   argument:

    + `even`: returns `true` if its argument is even, and `false` otherwise.

    function even (number) {
      if(number % 2 === 0) {
        return true;
      }
      else {
        return false;
      }
    }
    
    even(2); // true
    even(1); // false

    + `odd`: the opposite of the above.
 
    function odd (number) {
      if(number % 2 !== 0) {
        return true;
      }
      else {
        return false;
      }
    }
    
    odd(2); // false
    odd(1); // true

    + `positive`: returns `true` if its argument is positive, and `false` otherwise.

    function positive (number) {
      if(number > 0) {
        return true;
      }
      else {
        return false
      }
    }

    positive(2); // true
    positive(-1); // false

    + `negative`: the opposite of the above.

    function negative (number) {
      if(number < 0) {
        return true;
      }
      else {
        return false
      }
    }

    negative(2); // false
    negative(-1); // true

4. Write a function `sayHello` that takes a *language* parameter, and returns
   "hello" in that language. Make the function work with **at least three
   languages**.

   function sayHello (language) {
    if(language == "Portuguese") {
      return "OLA!";
    }
    else if (language == "Korean") {
      return "안영";
    }
    else if (language == "English") {
      return "HELLO!"
    }
   }

   sayHello("Portuguese"); // "OLA!"
   sayHello("Korean"); // "안영"
   sayHello("English"); // "HELLO!"


5. Write a function `validCredentials` that accepts two parameters: *username*
   and *password*, and returns `true` if **both** are long enough, and `false`
   otherwise. You can decide what constitutes "long enough".

   function validCredentials (username, password) {
    if (username.length >= 8 && password.length >= 8) {
      return true;
    }
    else {
      return false;
    }
   }

   validCredentials("ASDFASDF", "asdfasdf"); // true
   validCredentials("asdf", "sadfasdfasdf"); // false

6. **Repeating a String `n` Times:** Let's write a function called 
   `repeatString` that takes two parameters: a string `str`, which is the string
   to be repeated, and `count` -- a number representing how many times the
   string `str` should be repeated, *e.g.*

   
   function repeatString(str, count) {
     // TODO: your code here
     return str.repeat(count); 
   }
   
   OR
   
   function repeatString(str, count) {
      var rtn = '';
      for(var i = 0; i < count; i++) {
         rtn += str;
      }
      return rtn;
   }

   repeatString('dog', 0); // => ''
   repeatString('dog', 1); // => 'dog'
   repeatString('dog', 2); // => 'dog' + 'dog' => 'dogdog'
   repeatString('dog', 3); // => 'dog' + 'dog' + 'dog' => 'dogdogdog'
   

7. Write a function called `average` that takes an array of numbers as a
   parameter and returns the *average* of those numbers.

// TOOK ME A WHILE TO FIGURE THIS ONE OUT, PARTNER HELPED ME OUT WITH THIS ONE

   var arrayOfNumbers = []
   function average (numbers) {
    var total = 0;
    for (var i = 0; i < numbers.length; i++) {
      total += numbers[i]
    }
  return total/numbers.length;
}

average([1, 3, 4, 5, 6, 7])

8. Write a function `countWords` that, when given a string as an argument,
   returns an *object* where *keys* are the words in the string, and *values*
   are the number of occurrences of that word within the string:

// I HAD MAJOR DIFFICULTIES DOING THIS EXERCISE, I WILL PROBABLY NEED TO REVIEW THIS PROBLEM (from this point foward it was difficult to finish this checkpoint)
   
   function countWords(s) {
   // ...
   var s = s.split(" ");
   var result = {};
   for (var i = 0; i < s.length; i++) {
    if(result[s[i]] ){
      result[s[i]]++;
    }
    else {
      result[s[i]] = 1;
    }
   }
return result;
}
   countWords("hello hello"); // => {"hello": 2}
   countWords("Hello hello"); // => {"Hello": 1, "hello": 1}
   countWords("The quick brown"); // => {"The": 1, "quick": 1, "brown": 1}


   **HINT:** You will want to make use of the string method `split`. Try
   `\"Hello hello".split(" ")` at a console to see how it works.

   - Modify `countWords` to be *case insensitive* by using the following string
     method (experiment at a console with it to learn its behavior):

   
   "HElLo".toLowerCase(); // => "hello"

   
### Bonus

// I HAVEN'T REALLY TOUCHED THIS EXERCISE BUT WILL TRY TO TACKLE IT AGAIN.

1. Read about the join method on MDN and use it to implement a function that accepts a string
   as an argument and returns that string reversed.

2. The function `Object.keys` returns an array of an object's *keys*. Experiment
   with it at the console like this:

 
   Object.keys({a: 1, b: 2});

    function reverseString(str) {
    return str = str.split('').reverse().join('');
  }
  
  reverseString('abc');
   

   Using this property, write versions of the above functions using repetition
   through function invocation (*i.e.* recursion)