JavaScript - RegEx Example

This page will show a increasingly complex example. We will start simple and grow it's complexity.

And.... Introduce a little anarchy, upset the established order and everything becomes chaos. I'm an agent of chaos. Oh, and you know the thing about chaos? It's fair. - The Dark Knight, 2008

Looking for anarchy regardless of case. Will return position. This is a literal search.

// example 1
let pattern1 = /Anarchy/i;
let results1 = stringToSearch.search(pattern1);
document.getElementById("demo1").innerHTML = "Position of Anarchy: " + results1;

This uses a range. In this example, we are looking for any characters from a to z. The asterisk indicates we are looking for a match with any number of characters - starting at 1. The results are 0 as expected. It found a match in position "0".

// example 2
let pattern2 = /[a-z]*/i;
let results2 = stringToSearch.search(pattern2);
document.getElementById("demo2").innerHTML = results2;

This looks for a range of characters from a-z but will require the match which is found have 7 characters. This is done by using the {7} instead of the *.

let pattern3 = /[a-z]{7}/i;
let results3 = stringToSearch.search(pattern3);
document.getElementById("demo3").innerHTML = results3;

This example uses \b modifiers. This requires the match to be on a string boundary - it must be on the beginning of the string and/or the end of the string. Here, we are looking for the string 'thing' which must be in the beginning of the string or the end.

let pattern4 = /\bthing\b/i;
let results4 = stringToSearch.search(pattern4);
document.getElementById("demo4").innerHTML = results4;

This example uses a numeric range [0-9] and requires four characters. The match must be at the beginning or the end of the string.

let pattern5 = /\b[0-9]{4}\b/;
let results5 = stringToSearch.search(pattern5);
document.getElementById("demo5").innerHTML = results5;

This example uses a numeric range [0-9] and requires five characters which is common for finding a zipcode. In addition, it allows for a user or input to provide a plus-four zipcode. Since the input may or may not have the plus-four part, we need to account for that.

// example 6 - couldn't get this to work...
let stringToSearch2 = "My zip code is 23112-0000.";
let pattern6 = /\b[0-9]{5}(?:-[0-9]{4})?\b/;
let results6 = stringToSearch.search(pattern6);
document.getElementById("demo6").innerHTML = results6;

https://www.w3schools.com/js/js_regexp.asp

http://buildregex.com/

https://www.regexbuddy.com/create.html