javascript regex match

// Javascript Regex Reference
//  /abc/	A sequence of characters
//  /[abc]/	Any character from a set of characters
//  /[^abc]/	Any character not in a set of characters
//  /[0-9]/	Any character in a range of characters
//  /x+/	One or more occurrences of the pattern x
//  /x+?/	One or more occurrences, nongreedy
//  /x*/	Zero or more occurrences
//  /x?/	Zero or one occurrence
//  /x{2,4}/	Two to four occurrences
//  /(abc)/	A group
//  /a|b|c/	Any one of several patterns
//  /\d/	Any digit character
// /\w/	An alphanumeric character (“word character”)
//  /\s/	Any whitespace character
//  /./	Any character except newlines
//  /\b/	A word boundary
//  /^/	Start of input
//  /$/	End of input

<script> 
  
    // initializing function to demonstrate match() 
    // method with "i" para 
    function matchString() { 
        var string = "Welcome to GEEKS for geeks!"; 
        var result = string.match(/eek/i); 
        document.write("Output : " + result); 
    } matchString(); 
      
</script>                     

//Declare Reg using slash
let reg = /abc/
//Declare using class, useful for buil a RegExp from a variable
reg = new RegExp('abc')

//Option you must know: i -> Not case sensitive, g -> match all the string
let str = 'Abc abc abc'
str.match(/abc/) //Array(1) ["abc"] match only the first and return
str.match(/abc/g) //Array(2) ["abc","abc"] match all
str.match(/abc/i) //Array(1) ["Abc"] not case sensitive
str.match(/abc/ig) //Array(3) ["Abc","abc","abc"]
//the equivalent with new RegExp is
str.match('abc', 'ig') //Array(3) ["Abc","abc","abc"]

// The match() method searches a string for a match against a regular expression,
// and returns the matches, as an Array object.
// If the regular expression does not include the g modifier (to perform a global search),
// the match() method will return only the first match in the string.
// This method returns null if no match is found.

let str = "The rain in SPAIN stays mainly in the plain"; 
let res1 = str.match(/ain/g); /* ["ain", "ain", "ain"] */
let res2 = str.match(/ain/); /* ["ain", index: 5, input: "The rain in SPAIN stays mainly in the plain", groups: undefined] */
let res3 = str.match(/blah/); /* null */
 

const match = 'some/path/123'.match(/\/(\d+)/)
const id = match[1] // '123'

// Tests website Regular Expression against document.location (current page url)
if (/^https\:\/\/example\.com\/$/.exec(document.location)){
	console.log("Look mam, I can regex!");
}

//Adding '/' around regex
var regex = /\s/g;
//or using RegExp
var regex = new RegExp("\s", "g");

// Regular expression match sequence of characters
console.log(/abc/.test("abcde")); // true
console.log(/abc/.test("abxde")); // false

cadena = "Para más información, vea Capítulo 3.4.5.1";
expresion = /ver/i;
incluye = cadena.match(expresion);
console.log(incluye);