GDI JavaScript 201 Exercise

Welcome! This is the homework to accompany Girl Develop It LA's JavaScript 201: Intermediate JavaScript class. You can always reference the slides if you get stuck. Commit to spending at least 20 minutes trying to figure out a problem before you peek at the answer. It helps you learn!

1. Always Be True

Write a function that will filter all false and false-y values from an array

Sample Array: [null, 0, 17, false, -27, '', undefined, 47, null]

Expected Results: [17, -27, 47]

var myArray = [null, 0, 17, false, -27, '', undefined, 47, null];

function findTrue(elem) {
	return elem;
}

var trueArray = myArray.filter(findTrue);

console.log(trueArray);

2. Secret Code

Write a function that will take an array of letters and convert it to an array of numbers, so that A becomes 1, B becomes 2, C becomes 3, and so on.

Sample Array: ['f', 'a', 'b', 'u', 'l', 'o', 'u', 's']

Expected Result: [6, 1, 2, 21, 12, 15, 21, 19]

var myArray = ['f', 'a', 'b', 'u', 'l', 'o', 'u', 's'];

function secretMessage(elem) {
	var alphabet = 'abcdefghijklmnopqrstuvwxyz';
	var number = alphabet.indexOf(elem);

	return number + 1;
}

var numbers = myArray.map(secretMessage);

console.log(numbers);

3. Squares

Write a function that will take an array of numbers and return an array with the square of each number.

Sample Array: [3, 5, 7, 10]

Expected Results: [9, 25, 49, 100]

var myArray = [3, 5, 7, 10];

function squareNumbers(elem) {
	return elem * elem;
}

var squares = myArray.map(squareNumbers);

console.log(squares);

4. Secret Code Maker

Write a function that will take a message as a string and convert it to a string of numbers. Leave any spaces or punctuation.

Sample Message: This is a secret message. Don't tell anyone!

Expected Output:

20 8 9 19   9 19   1   19 5 3 18 5 20   13 5 19 19 1 7 5 .   4 15 14 ' 20   20 5 12 12   1 14 25 15 14 5 !

var message = 'This is a secret message. Don\'t tell anyone!';

var alphabet = 'abcdefghijklmnopqrstuvwxyz';
var messageArray = message.toLowerCase().split('');

function codeMessage(elem) {
	var code = alphabet.indexOf(elem) + 1;
	if (code == 0) {
		code = elem;
	}
	return code;
}

var encodedMessageArray = messageArray.map(codeMessage);
var encodedMessage = encodedMessageArray.join(' ');
console.log(encodedMessage);

5. Secret Message Decoder

Write a function that will take encoded messages from the previous function and convert them back to the original message.

Sample Message:

20 8 9 19   9 19   1   19 5 3 18 5 20   13 5 19 19 1 7 5 .   4 15 14 ' 20   20 5 12 12   1 14 25 15 14 5 !

Expected Output: This is a secret message. Don't tell anyone!

var secretMessage = '20 8 9 19   9 19   1   19 5 3 18 5 20   13 5 19 19 1 7 5 .   4 15 14 \' 20   20 5 12 12   1 14 25 15 14 5 !';

var alphabet = 'abcdefghijklmnopqrstuvwxyz';
var secretMessageArray = secretMessage.split(' ');

function isNumber(obj) {
	return !isNaN(parseFloat(obj));
}

function decodeMessage(elem) {
	var letter;
	if (isNumber(elem)) {
		letter = alphabet.charAt(elem - 1);
	} else if (elem == '') {
		letter = ' ';
	} else {
		letter = elem;
	}

	return letter;
}

var messageArray = secretMessageArray.map(decodeMessage);
var message = messageArray.join('');

console.log(message);

6. Show object info

Write a function that will print out all the properties of an object to the console.

Sample Object:

mabel = {
	temperament: 'needy',
	fur: 'gray',
	eyes: 'green',
	sounds: ['meow', 'purr', 'hiss']
};