3) Regular Expressions.js

// Using the Test Method
let myString = "Hello, World!";
let myRegex = /Hello/;
let result = myRegex.test(myString); 

// Match Literal Strings
let waldoIsHiding = "Somewhere Waldo is hiding in this text.";
let waldoRegex = /Waldo/;
let result = waldoRegex.test(waldoIsHiding);

// Match a Literal String with Different Possibilities
let petString = "James has a pet cat.";
let petRegex = /dog|cat|bird|fish/;
let result = petRegex.test(petString);

// Ignore Case While Matching
let myString = "freeCodeCamp";
let fccRegex = /freecodecamp/i;
let result = fccRegex.test(myString);

// Extract Matches
let extractStr = "Extract the word 'coding' from this string.";
let codingRegex = /coding/;
let result = extractStr.match(codingRegex);

// Find More Than the First Match
let twinkleStar = "Twinkle, twinkle, little star";
let starRegex = /twinkle/gi;
let result = twinkleStar.match(starRegex);

// Match Anything with Wildcard Period
let exampleStr = "Let's have fun with regular expressions!";
let unRegex = /.un/;
let result = unRegex.test(exampleStr);

// Match Single Character with Multiple Possibilities
let quoteSample = "Beware of bugs in the above code; I have only proved it correct, not tried it.";
let vowelRegex = /[aeiou]/gi;
let result = quoteSample.match(vowelRegex);

// Match Letters of the Alphabet
let quoteSample = "The quick brown fox jumps over the lazy dog.";
let alphabetRegex = /[a-z]/gi;
let result = quoteSample.match(alphabetRegex);

// Match Numbers and Letters of the Alphabet
let quoteSample = "Blueberry 3.141592653s are delicious.";
let myRegex = /[h-s2-6]/gi;
let result = quoteSample.match(myRegex);

// Match Single Characters Not Specified
let quoteSample = "3 blind mice.";
let myRegex = /[^aeiou^0-9]/gi;
let result = quoteSample.match(myRegex);

// Match Characters that Occur One or More Times
let difficultSpelling = "Mississippi";
let myRegex = /s+/gi;
let result = difficultSpelling.match(myRegex);

// Match Characters that Occur Zero or More Times
let chewieQuote = "Aaaaaaaaaaaaaaaarrrgh!";
let chewieRegex = /Aa*/;
let result = chewieQuote.match(chewieRegex);

// Find Characters with Lazy Matching
let text = "<h1>Winter is coming</h1>";
let myRegex = /<.*?>/;
let result = text.match(myRegex);

// Find One or More Criminals in a Hunt
let reCriminals = /C+/; // Change this line
let result = reCriminals.test(crime);

// Match Beginning String Patterns
let rickyAndCal = "Cal and Ricky both like racing.";
let calRegex = /^Cal/;
let result = calRegex.test(rickyAndCal);

// Match Ending String Patterns
let caboose = "The last car on a train is the caboose";
let lastRegex = /caboose$/;
let result = lastRegex.test(caboose);

// Match All Letters and Numbers
let quoteSample = "The five boxing wizards jump quickly.";
let alphabetRegexV2 = /\w/gi;
let result = quoteSample.match(alphabetRegexV2).length;

// Match Everything But Letters and Numbers
let quoteSample = "The five boxing wizards jump quickly.";
let nonAlphabetRegex = /\W/gi;
let result = quoteSample.match(nonAlphabetRegex).length;

// Match All Numbers
let numString = "Your sandwich will be $5.00";
let numRegex = /\d/gi;
let result = numString.match(numRegex).length;

// Match All Non-Numbers
let numString = "Your sandwich will be $5.00";
let noNumRegex = /\D/gi;
let result = numString.match(noNumRegex).length;

// Restrict Possible Usernames
let username = "JackOfAllTrades";
let userCheck =  /^[a-z][a-z]+\d*$|^[a-z]\d\d+$/i;
let result = userCheck.test(username);

// Match Whitespace
let sample = "Whitespace is important in separating words";
let countWhiteSpace = /\s/g;
let result = sample.match(countWhiteSpace);

// Match Non-Whitespace Characters
let sample = "Whitespace is important in separating words";
let countNonWhiteSpace = /\S/g;
let result = sample.match(countNonWhiteSpace);

// Specify Upper and Lower Number of Matches
let ohStr = "Ohhh no";  
let ohRegex = /Oh{3,6}\sno/;
let result = ohRegex.test(ohStr);

// Specify Only the Lower Number of Matches
let haStr = "Hazzzzah";
let haRegex = /Haz{4,}ah/;
let result = haRegex.test(haStr);

// Specify Exact Number of Matches
let timStr = "Timmmmber";
let timRegex = /Tim{4}ber/;
let result = timRegex.test(timStr);

// Check for All or None
let favWord = "favorite";
let favRegex = /favou?rite/;
let result = favRegex.test(favWord);

// Positive and Negative Lookahead
let sampleWord = "astronaut";
let pwRegex = /(?=\w{6})(?=\w*\d{2})/;
let result = pwRegex.test(sampleWord);

// Check For Mixed Grouping of Characters
let myString = "Eleanor Roosevelt";
let myRegex = /(Franklin|Eleanor).+Roosevelt/;
let result = myRegex.test(myString);

// Reuse Patterns Using Capture Groups
let repeatNum = "42 42 42";
let reRegex = /^(\d+) \1 \1$/;
let result = reRegex.test(repeatNum);

// Use Capture Groups to Search and Replace
let str = "one two three";
let fixRegex = /(\w+)\s(\w+)\s(\w+)/;
let replaceText = "$3 $2 $1";
let result = str.replace(fixRegex, replaceText);

// Remove Whitespace from Start and End
let hello = "   Hello, World!  ";
let wsRegex = /^\s+|\s+$/g;
let result = hello.replace(wsRegex, "");