GDI Intermediate JavaScript Exercise

Welcome! This is the homework to accompany Girl Develop It Seattle's 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']
};