Introduction to Regular Expressions With JavaScript



Regular expressions (RegExp) are a valuable and amazing piece of JavaScript. The motivation behind a RegExp is to decide if a given string worth is legitimate, in view of a lot of standards.

Such a large number of instructional exercises don’t really show you how to compose regular expressions. They basically give you a couple of models, a large portion of which are tragically hard to comprehend, and after that never clarify the subtleties of how the RegExp functions. On the off chance that you’ve been baffled by this also, at that point you’ve gone to the perfect spot! Today, you’re going to really figure out how to compose regular expressions.

Check here JavaScript Regular Expressions

To figure out how they work, we’re going to begin with an exceptionally basic model and afterward persistently add to the principles of the RegExp. With each standard that we include, I will clarify the new guideline and what it adds to the RegExp.

A RegExp is essentially a lot of guidelines to decide if a string is legitimate. How about we expect that we have a site page where our clients enter their date of birth. We can utilize a regular articulation in JavaScript to approve whether the date that they enter is in a substantial date design. All things considered, we don’t need them to enter something that isn’t a date.

Substring Search

In any case, how about we compose a RegExp that requires our clients to enter a date that contains this worth: “Blemish 16-1981”. Notice that they can enter anything they need, as long as the worth contains MAR-16-1981 some place in the worth. For instance, this would even be substantial with this articulation: TEST-MAR-16-1981-EXTRA.

The following is the HTML and JavaScript for a site page with a structure that enables our clients to enter their date of birth.

work validateDateFormat(inputString) {

var rxp = new RegExp(/MAR-16-1981/);

var result = rxp.test(inputString);

on the off chance that (result == false) {

alert(“Invalid Date Format”);


return result;


Observe the accompanying key bits of this code:

  1. When the submit catch is clicked, our JavaScript capacity is called. On the off chance that the worth bombs our test, we show an alarm spring up box with a mistake message. In this situation, the capacity likewise restores a bogus worth. This guarantees the structure doesn’t get submitted.
  2. Notice that we’re utilizing the RegExp JavaScript object. This article gives us a “test” technique to decide whether the worth passes our regular articulation rules.


As of not long ago, we’ve indicated scopes of letters [A-Z] and numbers [0-9]. There are an assortment of strategies for composing ranges inside regular expressions. You can determine a scope of [abc] to coordinate an or b or c. You can likewise determine a scope of [^abc] to coordinate whatever isn’t an or b or c.

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