How to Transfer Input Value from One Field to Another in JavaScript

Learn how to efficiently transfer the value of one input field to another with a minus sign in JavaScript without the need for a submit button.
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How to Transfer Input Value from One Field to Another in JavaScript

If you've ever worked with web forms, you may have encountered a scenario where you need to dynamically pass the value from one input field to another with some modifications. In this guide, we'll tackle a common challenge: how to transfer the value of the first input to the second input field, appending a minus sign (-) to it without needing to click a submit button.

The Problem

Imagine having a form with two input fields on a web page. You want the first input field to automatically update the second field with its value, but with a minus sign at the end. This functionality can enhance the user experience by eliminating the need for extra clicks. Here’s an example of what the requirement looks like:

First Input Field: Where the user enters a value (e.g., 100).

Second Input Field: Should automatically display 100- as soon as the value is inputted in the first field.

You may be using PHP and JavaScript for your web application, but here we’ll focus on the JavaScript aspect to achieve the desired functionality.

The Solution

To realize this functionality, we can leverage JavaScript to listen for changes in the first input field and then update the second field accordingly. Here’s how to implement it step by step:

Step 1: Setting Up Your HTML Structure

Create a straightforward HTML structure with two input fields. The first field will trigger the update in the second field.

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

Step 2: Understanding the JavaScript Function

Function Declaration: The function setSecondField(value) is defined to take the current value of the first input field.

Updating the Value: The value of the second input field is set by concatenating the value of the first field with a minus sign (-).

Step 3: Attaching the Function to the Input Event

In the first input field (<input type="text" name="title" id="field1">), we link our JavaScript function to the oninput event. This means every time a user types in the first field, the function gets executed and the second field updates automatically.

Conclusion

By following the above steps, you can effectively transfer the value from one input field to another in real-time using JavaScript. This small functionality can significantly improve the interaction and usability of your web forms.

Feel free to customize this code further to fit the specific needs of your web application!