JavaScript Regex          


A string of characters called a regular expression creates a search pattern. Text search and text replacement operations can both be performed using the search pattern.      

This blog will discuss in more detail how using regular expressions can benefit you in the programming world.  

JavaScript Validation 

Do you know what form validation is? JavaScript, a scripting language used for validation and verification, enters the picture at this point. JavaScript on web pages can be used to validate a form. It should be integrated with HTML. JavaScript is the fundamental technique to learn if you want to know how to comprehend the validations carried out on webpages, despite the fact that many other languages have entered the picture for validation.  

Validating the values submitted by the end-user during the submission of a form is known as form validation. Regular Expression is crucial in the process of validating a form. Let’s examine the meaning of a regular expression.

Regular Expression: An object that describes a pattern of characters is known as a regular expression. For pattern matching and search and replace operations on text, regular expressions are utilised. 

Therefore, JavaScript is quite important in this field for validating the values.

JavaScript Replace Regex

Regular Expressions, often known as RegEx, are a potent tool for text analysis. RegEx allows you to compare strings at specific positions where certain characters (like JavaScript) or patterns match. 

Strings in JavaScript can have characters substituted for certain parts of the string using the .replace method.  

This is a common way to use it: 

const str = Good morning;
const newStr = str.replace("ood", "-");
// G- morning 

In the example discussed above, the user needs to provide two arguments to the replace method. One is the string that needs to be replaced, and the other is the replacement string.

Regex is useful in this situation. The characters that must be replaced are “ood,” therefore the use of .replace above is restricted. How can you achieve replacing a combination of numbers, letters or many two or three symbols? 

This can be done using RegEx and the .replace function. RegEx works well for re-creating patterns. With this and .replace, you can easily replace entire patterns rather than just specific characters.

Formulation of Regular Expressions

There are two ways to build a regular expression in JavaScript:

The forward slashes /…/, used in the same way that quotes “” are used to create strings, signify that we are creating a regular expression pattern. 

If you are writing the code and you are aware of the regular expression pattern, you should use a regex literal. However, if the regex pattern needs to be generated dynamically, use the Regex function Object() { [native code] }.  

Additionally, using a template literal to create a pattern is possible with the regex function Object() { [native code] } but not with the literal regex syntax.

Using Regular Expressions 

Unique Characters 

A character with a reserved meaning is referred to as a special character in a regular expression. You can accomplish more than just finding a direct match when you use special characters. 

For instance, you can use special characters to match a character in a string that might or might not appear once or more than once. 

These characters fall under various subgroups that carry out related tasks.

How Do Character Classes Work?  

To match any one of several characters in a specific position, a character class is used. 

Use square brackets to indicate a character class, and list the characters you want to match inside the brackets. 

A Negated Character Class 

The caret symbol will match any character that isn’t listed inside the square brackets if you add it to a character class like this: […]. 


In a character class, the hyphen (-) denotes range. 

Let’s say you want to match a group of characters, like [abcdefg], or a group of numbers.  It can be expressed in the following ranges: [0-9] and [a-g], respectively.


Another method of specifying a group of options is through alternation. The pipe character | is used to match any of the subexpressions in this case. 

An alternative is a subexpression that can be either of the two. The “or” symbol represented by the pipe matches a number of possibilities. You can use subexpressions in combination as an alternative.


As an illustration, (x|y|z)a will match xa, ya, or za.

You can use parentheses to group the alternatives together to constrict the scope of the alternation.

x|y|za would mean either x or y or za without the parentheses. 


In the end, it is up to you to decide if working with regular expressions in JavaScript is worth the effort. As we demonstrated earlier, they can be useful for many scenarios, and we believe the techniques shown here will at least help you find your way around this powerful but complex syntax.

5 Day Coding Challenge – learn JavaScript basics

Code Institute’s free 5 Day Coding Challenge can offer you some insights into HTML, CSS & JavaScript. The best thing about the challenge, other than learning the basics, is that it’ll let you know if you have an aptitude for software development. Register for this weekly challenge through the form below. Alternatively, if you want to learn more about our Full Stack Software Development programme, follow this link

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