How to Change the Value of Two Input Fields in a Form with JavaScript or jQuery

Learn how to dynamically update date fields in a form using `JavaScript` and `jQuery`. This guide will teach you how to subtract days from the current date and input those values into your form.
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Changing the Value of Two Input Fields Using JavaScript or jQuery

When working with forms in web development, there often comes a time when you need to programmatically change the values of input fields based on user interactions. This guide will address a common scenario: updating two date fields in a form using JavaScript or jQuery when the user clicks on buttons.

The Challenge: Dynamic Date Input

You have a form containing two date input fields—let's call them date1 and date2. The requirement is simple: when a button is clicked, you want to:

Insert the current date into the date2 field.

Insert the current date minus a certain number of days into the date1 field.

To provide a practical example, clicking a button labeled "3 Days" should set date2 to today’s date and date1 to three days before today.

Setting Up the HTML Structure

Here’s how you can structure your HTML form:

[[See Video to Reveal this Text or Code Snippet]]

The JavaScript Functionality

We'll use jQuery to make it easier to manipulate the DOM and handle events. Below is the code that will handle the logic for updating the input fields:

[[See Video to Reveal this Text or Code Snippet]]

How It Works

Calculate Current Date: The function updateDefaults(daysCount) calculates today’s date using the Date() object.

Format the Date: The date is formatted to the required format ("YYYY-MM-DD").

Set Dates in Input Fields: The calculated dates are then inserted into the respective input fields using jQuery’s .val() method.

Button Click Events: Each button is wired up to call the updateDefaults() function with the specified number of days.

Conclusion

With the above steps, you can easily manipulate the values of two input fields in a form based on button clicks using JavaScript and jQuery. This functionality enhances user experience, providing real-time updates without requiring page reloads.

If you're new to web development, this simple example is a great way to begin understanding how JavaScript can interact with HTML, enabling dynamic and interactive web pages.