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rexfordkelly-at-makersquare/W2D2 Checkpoint.js

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Last active August 25, 2016 00:55
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W2D2 Checkpoint.js
# W2D2 Checkpoint
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) {// Good Job!
return ((num1 + num2) / 2) // do we need the wrapping parens?
}
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) { // Good Job!
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) { // Good Job!
if(number % 2 === 0) {
return true;
}
else {
return false;
}
}
even(2); // true
even(1); // false
+ `odd`: the opposite of the above.
function odd (number) { // Good Job!
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) { // Good Job!
if(number > 0) {
return true;
}
else {
return false
}
}
positive(2); // true
positive(-1); // false
+ `negative`: the opposite of the above.
function negative (number) { // Good Job!
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) { // Good Job!
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) { // Good Job!
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.*
```js
function repeatString(str, count) {
// TODO: your code here
return str.repeat(count);
}
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) { // Good Job!, try and keep you spacing and formating consistent
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)
```js
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):
```js
"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:
```js
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)
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