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Version: v1.2

✏️ 1.2.1.1 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 diving 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.

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​

Answer 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.)

Work 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.