Reference of some common regular expression meta characters

regExCharacterReference

let re;
// Literal Characters
re = /hello/;
re = /hello/i;

// Metacharacter Symbols
re = /^h/i; // Must start with
re = /world$/i; // Must end with
re = /^hello$/i;  // Must begin and end with
re = /h.llo/i; // Can match any one character - .
re = /h*llo/i; // Can match any character 0 or more times - *
re = /gre?a?y/i; // optional character
re = /gray\?/i; // Escape character

// Brackets [] - Character Sets
re = /gr[ae]y/i; // Must be an a or e
re = /[GF]ray/; // Must be a G or F
re = /[^GF]ray/; // Match anything except a G or F
re = /^[GF]ray/; // Match start with 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]ray/i; // Match any digit

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

// Parentheses () - Grouping
re = /([0-9]x){3}/; // Matches 3x three times = '3x3x3x'
re = /^([0-9]x){3}$/; // Must begin and end, so exaclty 3x3x3x

// Shorthand Character Classes
re = /\w/; // Word chracter = alphanumeric or _
re = /\w+/; // + equals one or more
re = /\W/; // Non-Word characters. Non alphanumeric or _
re = /\d/;  // Match any digit
re = /\d+/;  // Match any digit one or more times
re = /\D/; // Non-digit
re = /\s/; // Match white space char
re = /\S/; // Match non-white space char
re = /Heaven\b/; // Word boundary

// Assertions
re = /x(?=y)/; // Match x only if followed by y
re = /x(?!y)/; // Match x only if not followed by y


// String to match
const str = `Heaven xy`;

// 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);