Key Concepts

Review core concepts you need to learn to master this subject

Character Sets in Regular Expressions

Optional Quantifiers in Regular Expressions

Literals in Regular Expressions

Fixed Quantifiers in Regular Expressions

Alternation in Regular Expressions

Anchors in Regular Expressions

Regular Expressions

Wildcards in Regular expressions

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Character Sets in Regular Expressions

Regular expression character sets denoted by a pair of brackets [] will match any of the characters included within the brackets. For example, the regular expression con[sc]en[sc]us will match any of the spellings consensus, concensus, consencus, and concencus.

Introduction to Regular Expressions
Lesson 1 of 1
  1. 1
    Introduction
    When registering an account for a new social media app or completing an order for a gift online, nearly every piece of information you enter into a web form is validated. Did you enter a properly f…
    Start
  2. 2
    Literals
    The simplest text we can match with regular expressions are literals. This is where our regular expression contains the exact text that we want to match. The regex a, for example, will match …
    Start
  3. 3
    Alternation
    Do you love baboons and gorillas? You can find either of them with the same regular expression using alternation! Alternation, performed in regular expressions with the pipe symbol, |, allows…
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  4. 4
    Character Sets
    Spelling tests may seem like a distant memory from grade school, but we ultimately take them every day while typing. It’s easy to make mistakes on commonly misspelled words like consensus, and on t…
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  5. 5
    Wild for Wildcards
    Sometimes we don’t care exactly WHAT characters are in a text, just that there are SOME characters. Enter the wildcard .! Wildcards will match any single character (letter, number, symbol or …
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  6. 6
    Ranges
    Character sets are great, but their true power isn’t realized without ranges. Ranges allow us to specify a range of characters in which we can make a match without having to type out each ind…
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  7. 7
    Shorthand Character Classes
    While character ranges are extremely useful, they can be cumbersome to write out every single time you want to match common ranges such as those that designate alphabetical characters or digits. To…
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  8. 8
    Grouping
    Remember when we were in love with baboons and gorillas a few exercises ago? We were able to match either baboons or gorillas using the regex baboons|gorillas, taking advantage of the | symbol. Bu…
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  9. 9
    Quantifiers - Fixed
    Here’s where things start to get really interesting. So far we have only matched text on a character by character basis. But instead of writing the regex \w\w\w\w\w\w\s\w\w\w\w\w\w, which would mat…
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  10. 10
    Quantifiers - Optional
    You are working on a research project that summarizes the findings of primate behavioral scientists from around the world. Of particular interest to you are the scientists’ observations of humor in…
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  11. 11
    Quantifiers - 0 or More, 1 or More
    In 1951, mathematician Stephen Cole Kleene developed a system to match patterns in written language with mathematical notation. This notation is now known as regular expressions! In his honor, the…
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  12. 12
    Anchors
    When writing regular expressions, it’s useful to make the expression as specific as possible in order to ensure that we do not match unintended text. To aid in this mission of specificity, we can u…
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  13. 13
    Review
    Do you feel those regular expression superpowers coursing through your body? Do you just want to scream ah+ really loud? Awesome! You are now ready to take these skills and use them out in the wild…
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