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JavaScript 4 - Loops

Projected Time

About 2 hours

  • 40 minutes minutes for lesson slides
  • 40 minutes for Guided Practice
  • 40 minutes for Independent Practice
  • 20 minutes for Check for Understanding

Prerequisites

Motivation

JavaScript is used on the frontend of almost every website. It's also a widely-used scripting language that is used on the backend as well. The JavaScript lessons set a solid foundation in JavaScript basics so we can use the language in more robust ways in later lessons.

Objectives

Participants will be able to:

  • Write proper JavaScript for loop syntax
  • Iterate through an array using a for loop
  • Write proper JavaScript while loop syntax
  • Increment a counter variable properly inside a while loop

Specific Things to Learn

  • For loop syntax
  • Reasons to use a for loop
  • While loop syntax
  • Reasons to use a while loop

Lesson

Video walkthrough of lesson slides JavaScript 4 - Loops (20 min)

Read through lesson slides JavaScript 4 - Loops

Things to Remember

  • You'll get stuck in an infinite while loop if you don't increment or decrement the counter variable.

  • When using a for loop, remember that list indexing starts at zero!

Guided Practice

Work through this lesson on JS loops (about 30 min): https://www.codecademy.com/courses/introduction-to-javascript/lessons/loops/exercises/loops?action=resume_content_item

Independent Practice

Open REPL.it.

Activity 1 - Vacation Time!

Write a function called printVacations whose input is an array of arrays. Each sub-array should have two strings as elements: The 0th element should be a person's name and the 1st element should be that person's most desired vacation destination. Include a minimum of 3 sub-arrays in your input array, like so:

[ ['Tammy', 'Tahiti'], ['Erin', 'Banff, Alberta, Canada'], ['Janet', 'London'] ]

Your function should print each person's name and desired destination in a complete sentence, like this:

Tammy really wants to go to Tahiti.
Erin really wants to go to Banff, Alberta, Canada.
Janet really wants to go to London.

Activity 2 - Vacation Choices

Follow the prompt for Activity #1, but use this format for the input array instead:

[ ['Tammy', ['Tahiti', 'Bali', 'Hawaii']], ['Erin', ['Banff, Alberta, Canada', 'Iceland']], ['Janet', ['London', 'Hogwarts']] ]

The output should look similar to this:

Tammy is willing to go to Tahiti, Bali or Hawaii.
Erin is willing to go to Banff, Alberta, Canada or Iceland.
Janet is willing to go to London or Hogwarts.

Challenge

  • Write a program in JavaScript to print Multiplication table of given number using for loop. Also try the program using while loop.

Supplemental Materials

For Loops

While Loops

Check for Understanding

  • Differentiate between for loop and while loop.
  • Write down the syntax of a Nested for loop in JavaScript.
  • Convert the given while loop to a for loop:
let ourArray = [];
let i = 0;
while(i < 5) {
ourArray.push(i);
i++;
}
console.log(ourArray)