Nate Hart's Checkpoint 1

checkpoint1.js

/*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;
}

/*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 "Well hello there, " + name;
}

/*Write the following functions that each accept a single number as an argument:
		even: returns true if its argument is even, and false otherwise.
		odd: the opposite of the above.
		positive: returns true if its argument is positive, and false otherwise.
		negative: the opposite of the above.
*/

function even(n) {
	return n % 2 === 0;
}

function odd(n) {
	return n % 2 !== 0;
}

function positive(n) {
	return n > 0;
}

function negative(n) {
	return n < 0;
}

/*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(lang) {
	lang = lang.toLowerCase();
	if (lang === "spanish")
		return "hola";
	if (lang === "french")
		return "bonjour";
	if (lang === "hebrew")
		return "shalom";
	return "I don't speak " + lang;
}

/*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) {
	minUserNameLength = 6;
	minPasswordLength = 8;
	return username.length >= minUserNameLength && password.length >= minPasswordLength;
}

/*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.

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

function repeatString(str, count) {
	var newStr = "";
	for (var i = 0; i < count; i++) {
		newStr = newStr + str;
	}
	return newStr;
}

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

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

/*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:*/

function countWords(str) {
	str = str.toLowerCase()
	var arr = str.split(" ");
	var wordObj = {};
	for (var i = 0; i < arr.length; i++) {
		if (wordObj[arr[i]] === undefined)
			wordObj[arr[i]] = 0;
		wordObj[arr[i]]++
	}
	return wordObj;
}

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

/*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.*/

function reverse(str) {
	var arr = str.split("");
	var newArr = [];
	for (var i = 0; i < arr.length; i++) {
		newArr[i] = arr[arr.length - i - 1];
	}
	return newArr.join("");
}

/*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});

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