Lesson 1.0.1 - Variables, Functions, and Strings

• Lesson 1.0.1 - Variables, Functions, and Strings
• Before we start
  • nodemon
  • playground.js
• Question 1: Advanced Greet
• Question 2: squishRepeat
• Question 3: capitalizeSentence
• Question 4: copyFromTheLastChar
• Question 5: replaceEveryGivenLetterWithWord
• Question 6: capitalizeIndex
• Question 7: hasOnlyOneOfThisLetter
• Question 8: MODIFY - Convert declarations to arrows
• Question 9: MODIFY - Explicit to implicit returns
• Question 10: DEBUG - Fix our mess of a function

Alright, for tonight's assignment we have all three coding types ("from scratch", "modify", and "debug") but no short answers. Get started with npm i to install all dependencies and be sure to run your tests frequently.

If you're ever confused about what a function should do, check the test files!

Before we start

nodemon

It can get pretty tedious having to manually rerun our scripts all the time. It's why we recommend test:w when developing, those restarts on save are super nice.

But, there's a way to get node to auto restart too. If you use the nodemon package to run your scripts, it will automatically rerun the file on save. We're using it for our playground.js script. Check it out!

Usually, people install it globally, but we have it as dev a dependency. That's primarily because we're making HW assignments, and if any bugs occur, we want to know all students are using the same version.

playground.js

This time we were even nicer, and imported all the from-scratch functions for you. We recommend using npm run playground to mess around with your work, and then npm run test:w when you get closer to the answers.

---

Question 1: Advanced Greet

Write a function advancedGreet that takes two parameters: a string name and a string mood. It should return the string:

"Hello [name], are you feeling [mood] today?"

Here's the catch, you must use string templates and not concatenation.

Question 2: squishRepeat

Write a function, squishRepeat that takes three parameters: a string str, a number index, and a number num. It should return a string that is created by taking a slice of the original string up to the index, and repeated num times.

NOTE: We will never give an index greater than the length of the string.

squishRepeat('hello', 1, 3)
// 'hhh'
squishRepeat('hello', 2, 3)
// 'hehehe'
squishRepeat('neato', 4, 2)
// 'neatneat'
squishRepeat('wow', 3, 4)
// 'wowwowwowwow'

To do this, it's highly recommended that you use the built in string method .repeat. Just give the docs a quick read, and you'll be set!

Question 3: capitalizeSentence

Write a function .capitalizeSentence() that takes one parameter: a string sentence. The function should return the sentence with only the first letter modified to be capitalized.

NOTE: The sentence we give you will always be a normal length, and will always have a letter as the first character.

capitalizeSentence('hello there!')
// Hello there!

Question 4: copyFromTheLastChar

Write a function copyFromTheLastChar that takes two parameters: a string str and character letter. The function should return a copy of the given str from the letter to the end of the str. If the letter appears in the string more than once, copy from the last one. If the given letter is the last letter of the string, simply return the letter.

NOTE: the letter we give will ALWAYS appear in the given string at least once.

copyFromTheLastChar('hello', 'e')
// ello
copyFromTheLastChar('hello', 'l')
// lo
copyFromTheLastChar('zzzzzz', 'z')
// z

Question 5: replaceEveryGivenLetterWithWord

Write a function replaceEveryGivenLetterWithWord that takes three parameters: a string str, a character letter, and a string word. Return a string where you have replaced every instance of that letter in the str with the given word. If the letter does not appear in the str, return the original str.

NOTE: the str, letter, and word will all be lowercase.

replaceEveryGivenLetterWithWord('hello', 'l', 'world')
// 'heworldworldo');
replaceEveryGivenLetterWithWord('I know you', 'k', "wow")
// "I wownow you");
replaceEveryGivenLetterWithWord('zoo', 'x', 'albatross')
// 'zoo');

Question 6: capitalizeIndex

Write a function capitalizeIndex that takes two parameters: a string word and a number index. The word will have no punctuation or spaces, and will be all lower case. Return the word, with the letter at the index capitalized.

NOTE: The given index will only ever be in the range from 0 to str.length - 1.

capitalizeIndex('hello', 0)
// 'Hello'
capitalizeIndex('hello', 1)
// 'hEllo'
capitalizeIndex('hello', 2)
// 'heLlo'
capitalizeIndex('hello', 3)
// 'helLo'
capitalizeIndex('hello', 4)
// 'hellO'

Question 7: hasOnlyOneOfThisLetter

Write a function hasOnlyOneOfThisLetter that takes two parameters: a string str and a character letter. Return the boolean true if the given letter appears only once, and false if it appears more than once.

NOTE: We will always give a letter that appears at least once in the string.

Question 8: MODIFY - Convert declarations to arrows

Inside declarations-to-arrow.js we have a few function declarations (and one old school function expression). Convert each of the functions to arrow function expressions, while maintaining exactly the same functionality.

⚠️ Note: To pass the tests, you will also need to update the names of the functions. Take a look at src/modify-spec.js where we define our tests and find in the code where we import the functions from declarations-to-arrow.js. That will give you a hint for what we want the function names to be.

Question 9: MODIFY - Explicit to implicit returns

Now in explicit-to-implicit.js, we have those same functions simplified so they only return things. Let's convert them to arrow functions again and make them have implicit returns.

⚠️ Note: To pass the tests, you will also need to update the names of the functions. Take a look at src/modify-spec.js where we define our tests and find in the code where we import the functions from explicit-to-implicit.js. That will give you a hint for what we want the function names to be.

Question 10: DEBUG - Fix our mess of a function

Inside bad-hoist.js we have a doozy of a function. It's declaring variables with var, using implicit globals, has sloppy concatenation, and trying (poorly) to hoist variables into a message. Ugh.

Right now it logs:

Hello undefined, are you feeling undefined today?
Oh no, I'm sorry you're feeling happy today.

Make it so it logs:

Hello Zo, are you feeling happy today?
Oh no, I'm sorry you're feeling sad today.

Fix the function so:

• var is not used
• implicit globals are not used
• const and let are used correctly
• We use templates over concatenation
• we still have 4 variable assignments: 3 initializations and 1 reassignment
  • Basically, you can't just remove all the code and console.log those two strings.