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JavaScript 8 - Regular Expressions / RegEx

Projected Time

About 2 hours

  • 20 minutes for video walkthrough of slides
  • 80 minutes for Independent Practice
  • 20 minutes for checking understanding

Prerequisites

Motivation

  • Regular Expressions allow you to search and modify strings using a special language. They are very powerful and can enable writing significantly less code.

  • Most online registration forms use RegEx to verify that the information entered is in the right format

  • Build/test tools match file names and extensions using regexes. For example, Jasmine uses regex to find test files ending in "spec.js".

Objectives

Apprentices will be able to:

  • Read and write RegEx in JavaScript
  • Use RegEx to test and replace strings
  • Understand basic regular expression special characters: .*+?\w\d

Specific Things to Learn

  • JavaScript's RegExp syntax/structure
  • Basic regular expression characters
  • How RegExp modifiers work
  • The 4 string methods and 2 RegExp methods that work with RegExps

Lesson

Instructor demonstrates in the video walk through how to work with Regular Expressions in JavaScript.

JavaScript VII (video)

JavaScript VII (slides)

Things to Remember

  • There are two ways to use RegEx:
    • RegEx as input to 4 String methods: String.replace(), String.match(), String.search(), String.split()
    • String as input to 2 RegEx methods: RegExp.test(), RegExp.exec()
  • You can add modifiers to RegEx
  • The pattern goes between the two forward slashes, and you can use back slashes to escape special characters
  • There are a lot of complex RegEx patterns. We'll teach the basic ones, but there are many more you can learn as you go.

Supplemental Materials

Independent Practice

  • Go through the tutorial at https://regexone.com. Do at least lessons 1-10. This isn't JavaScript specific, but it will help you understand how to match text with regular expressions.
  • Write a JavaScript function that takes a word and returns true if the word ends with tonica
  • Write a function expression that takes a string replaces all instances of symantec with semantic
  • Write a function that takes a string and deletes all words that end in ing
  • Write a function that takes a string and returns true if it is an email address. Compare your answer with your neighbor.
  • Write a function that takes a string containing names separated by commas like "Leah, Russell, Michelle" and returns an array of names, ["Leah", "Russell", "Michelle"]

Challenges

  • Write a regular expression that matches any Techtonica apprentice's first name, but not any staff members' first name.
  • Write a regular expression that matches all even-length strings but not odd-length ones.
  • Do lessons 11+ on https://regexone.com

Check for Understanding

  • Make a cheat sheet to remind yourself about the different regular expression characters and how to use them.
  • What character matches the beginning of the line?
  • What does the 'i' flag mean and what is it used for?
  • What does the dot ( . ) represent in Regex?
  • What are the advantages and disadvantages of using regex?