Creating currency mask with regular expressions
Posted: Sun Feb 02, 2025 3:54 am
Regular expressions can help us in several ways, one of which is by creating a monetary mask so that users have a more intuitive field when entering data. In addition to making the field easier to understand, it helps us avoid the user entering unwanted characters. In this article, we will use regular expressions to create a function that will do this entire process for us.
What are regular expressions?
Regular expressions are search patterns that allow you to find and manipulate text based on specific rules. They are an essential tool for parsing strings, validating input, and replacing specific parts of text. Using metacharacters like o .(dot) to represent any character and quantifiers like o *(asterisk) to indicate “zero or more occurrences,” you can create complex patterns to perform tasks like finding keywords in text or validating data formats like email addresses.
Additionally, they can be used to extract information from chinese america data documents, perform bulk replacement operations, and ensure the integrity of input data. Understanding and effectively applying regular expressions are valuable skills for developers, allowing them to address text manipulation challenges in an accurate and automated way, saving time and effort in programming.
Starting the monetary mask
Initially, the mask we will create will consist of creating a function, this function will be inserted into the HTML tag itself through the event onkeyup. This event executes the function every time the user releases the keystroke. The complete element in the HTML will look like this:
In this context, the keyword thisrefers to the HTML element that is triggering the event onkeyup, in this case, itself input.
This is useful because it allows the function to mascaradirectly access and manipulate the text input field that the user is typing into, without needing to select it through the JavaScript DOM (Document Object Model)this . Therefore, it is a convenient way to reference the current HTML element within the context of the event, making it easier to interact with it in JavaScript code .
JavaScript - Manipulating HTML elements in the DOM
Course
JavaScript - Manipulating HTML elements in the DOMKnow the course
Mask logic
With the HTML part ready, let's move on to our function. The function mascarawill have a single parameter, which will be the element itself, as we saw previously. In the parameters we can give it whatever name we want, I'll give it the name valor, so our function will look like this:
Copy
function mascara(valor) {}
First, we will capture the value that is inserted inside the input, since we have access to the element through the parameter, it is easy to capture this value. We will assign the value inserted inside a variable to make it easier to manipulate in the future. We do this through the property .value, like this:
From now on, everything that the user types in this element will be contained within the variable valorAlterado. First, we will use regular expressions to prevent the user from entering non-numeric values in this field. We do this using the replace()JavaScript method.
What are regular expressions?
Regular expressions are search patterns that allow you to find and manipulate text based on specific rules. They are an essential tool for parsing strings, validating input, and replacing specific parts of text. Using metacharacters like o .(dot) to represent any character and quantifiers like o *(asterisk) to indicate “zero or more occurrences,” you can create complex patterns to perform tasks like finding keywords in text or validating data formats like email addresses.
Additionally, they can be used to extract information from chinese america data documents, perform bulk replacement operations, and ensure the integrity of input data. Understanding and effectively applying regular expressions are valuable skills for developers, allowing them to address text manipulation challenges in an accurate and automated way, saving time and effort in programming.
Starting the monetary mask
Initially, the mask we will create will consist of creating a function, this function will be inserted into the HTML tag itself through the event onkeyup. This event executes the function every time the user releases the keystroke. The complete element in the HTML will look like this:
In this context, the keyword thisrefers to the HTML element that is triggering the event onkeyup, in this case, itself input.
This is useful because it allows the function to mascaradirectly access and manipulate the text input field that the user is typing into, without needing to select it through the JavaScript DOM (Document Object Model)this . Therefore, it is a convenient way to reference the current HTML element within the context of the event, making it easier to interact with it in JavaScript code .
JavaScript - Manipulating HTML elements in the DOM
Course
JavaScript - Manipulating HTML elements in the DOMKnow the course
Mask logic
With the HTML part ready, let's move on to our function. The function mascarawill have a single parameter, which will be the element itself, as we saw previously. In the parameters we can give it whatever name we want, I'll give it the name valor, so our function will look like this:
Copy
function mascara(valor) {}
First, we will capture the value that is inserted inside the input, since we have access to the element through the parameter, it is easy to capture this value. We will assign the value inserted inside a variable to make it easier to manipulate in the future. We do this through the property .value, like this:
From now on, everything that the user types in this element will be contained within the variable valorAlterado. First, we will use regular expressions to prevent the user from entering non-numeric values in this field. We do this using the replace()JavaScript method.