Скачать или смотреть How to Autofill an HTML Form Input Field Using JavaScript

Discover how to automatically populate an HTML form input field with a JavaScript function when values change in other fields. Perfect for any web developer looking to enhance user experience!
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This video is based on the question https://stackoverflow.com/q/74309167/ asked by the user 'Tomas' ( https://stackoverflow.com/u/19887229/ ) and on the answer https://stackoverflow.com/a/74309338/ provided by the user 'Evgeni Dikerman' ( https://stackoverflow.com/u/1761692/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Autofill an HTML Form Input Field Using JavaScript

If you’ve ever encountered the need to streamline your user input processes on a web page, you know how impactful it is to provide autofill functionalities. In this post, we're going to tackle a common scenario where you want to automatically fill in a price based on selections and inputs from other fields. Let’s break down the solution into simple, manageable sections.

Understanding the Problem

When building a web form, you may want to calculate values dynamically based on user input from multiple fields. In our scenario, the user selects an item and level, and inputs a duration (in hours). The goal is to automatically display the calculated price when the user makes any selection or input.

Here's a quick overview of our inputs:

Item: A drop-down menu to select an item.

Level: Another drop-down to select a level.

Duration: An input field where the user specifies hours.

Preliminary Price: A read-only input that displays the calculated price.

Solution Overview

To achieve this, we’ll need to create a JavaScript function that listens for changes in our form fields. The function will calculate the price based on the selected values and show it in the designated input field.

Step-by-Step Implementation

1. Set Up Your HTML Structure

Here’s the HTML code we’re working with:

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

2. Write the JavaScript Function

Now, let’s create the JavaScript function that will carry out our calculations:

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

Explanation of the JavaScript Code

Selecting Elements: We use document.getElementById to access our form fields.

Event Listener: We attach a change event listener to each of the dropdowns and the input field. This means whenever the user makes a selection or enters a number, our Calculate function will be triggered.

Calculate Function: Inside the function:

We retrieve the current values of the selected options and the number of hours entered.

We then compute the price by multiplying these values. This value is immediately reflected in the price field.

Conclusion

Adding an autofill feature to your HTML forms can greatly enhance the user experience by eliminating the need for manual calculations. By following the steps above, you can set up a live price calculation that updates as soon as your users make selections.

Implementing such functionalities not only makes your forms more interactive but also reduces input errors, making for a more seamless data entry process for users.

Happy coding!