ncatalin
3/8/2018 - 4:32 PM

Regular Expressions [Part 3] - Character Sets & Quantifiers

Modern JavaScript From The Beginning from Brad Traversy

app.js
content_copyfile_download
let re;
// Literal Characters
re = /hello/;
re = /hello/i;

// Metacharacter Symbols
re = /^h/i;           // Must start with
re = / world$/i;     // Must ends with
re = /^hello$/i;     // Must begin and end with
re = /h.llo/i;      // Matches any ONE character
re = /h*llo/i;      // Matches any character 0 or more times
re = /gre?a?y/i;    // Optional character
re = /gre?a?y\?/i;    // Escape character 


// Brackets [] - Character Sets
re = /gr[ae]y/i;      // Must be an a or e
re = /[GF]ray/i;      // Must be a G or F
re = /[^GF]ray/i;      // Match anything except a G or F
re = /[A-Z]ray/;      // Match any uppercase letter
re = /[a-z]ray/;      // Match any lowercase letter
re = /[A-Za-z]ray/;   // Match any  letter
re = /[0-9][0-9]ray/;      // Match any digit

// Braces {} - Quantifiers
re = /Hel{2}o/i;      // Must occur exactly {m} amount of times
re = /Hel{2,4}o/i;      // Must occur exactly {m} amount of times
re = /Hel{2,}o/i;      // Must occur at least {m} times

// Paretheses () - Grouping
re = /^([0-9]x){3}$/

// String to match
const str = '3x3x3x';

// Log Results
const result = re.exec(str);
console.log(result);

function reTest(re, str) {
  if(re.test(str)) {
    console.log(`${str} matches ${re.source}`);
  } else {
    console.log(`${str} does NOT match ${re.source}`);
  }
}

reTest(re, str);
index.html
content_copyfile_download
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>JavaScript Sandbox</title>
</head>
<body>
  
  <script src="app.js"></script>
</body>
</html>