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✏️ Practice: Review of JavaScript Basics

Goal: Discuss and apply these JavaScript concepts with your pair:

  • Operators
  • Using MDN documentation
  • String methods
  • JavaScript conventions
  • Data type detection and conversion

Reminder: Use the browser DevTools console to try out your JS code! If you need a review, read the instructions on how to use and pair program with the DevTools console in this lesson.

Code​

Work through each section of this practice lesson, switching who's driving and who's observing between each prompt.

Operators​

Use MDN documentation to learn about the remainder operator %, also known as "modulo":

  • Find the reference page for the remainder operator using Google or MDN's search.
  • Read the description and examples.
  • Use the built-in console to try out the remainder operator.

Make sure everyone understands what the remainder operator does, then work through these questions:

  • What is the % operator? How is the action it performs different from simply dividing?
  • Name 3 different types of operators and give an example of each.
  • What does console.log() do?
  • What is an operand? (Hint: this is not JavaScript-specific terminology.)

Find the remainder of the following expressions by dividing the two operands:

  • 1008 by 7
  • 23423 by 75
  • 90 by 3
  • 9,870,834,205,987 by 324

String Methods​

Find the reference page on MDN for the String.prototype.trim() method. Read through the description and examples. Use the built-in console to try out this string method.

Switch who's driving and observing for this next prompt. Find the reference page on MDN for the String.prototype.replace() method. Read through the description and examples. Note — ignore the references to regex; we'll learn about regex in coming weeks. Use the built-in console to try out this string method.

JavaScript Conventions​

Take turns answering these questions:

  • How are we supposed to name our variables in JavaScript?
  • What is the difference between a JavaScript expression and a JavaScript statement?
  • When should we include semicolons at the end of our lines of code?
  • When should we use let and when should we use const to declare a variable?

Data Type Detection and Conversion​

  • What are the two main categories of data types?
  • What is undefined?
  • What data type is NaN? What about Infinity? (Hint: if you are stuck, try detecting the data type.)

Take turns working through these prompts:

  • Set a variable called favNum equal to your favorite number and check the data type.
  • Then, create a new variable called stringNum converting the previous variable to a string. Check the data type again.
  • Next, create a third variable called parsedBackToNum, converting this string variable back to a number. Check the data type one more time.
  • Compare the first and third variables (favNum and parsedBackToNum) using === to confirm that they are equal.
  • Compare the first and second variables (favNum and stringNum) or second and third variables (stringNum and parsedBackToNum) to confirm that they are NOT equal.