What You'll Build

A dynamic form that demonstrates computed values - fields that automatically update based on other field values. You'll create a full name from first and last name, and real-time character counters.

What You'll Learn

How to create computed values that update automatically
Real-time text concatenation and formatting
Building dynamic character and word counters
Understanding reactive form behavior

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Interactive Learning

Every code snippet below is fully editable! Feel free to modify the code, experiment with different values, and see your changes reflected instantly in the live preview on the right.

Use the play button to run different snippet, or the refresh button to restore the original example.

Tutorial Steps

Step 1: Starting Point

Let's start with an empty form function. This is where we'll build our dynamic form with computed values step by step.

Step 2: Basic Input Fields

First, let's add the basic input fields that we'll use as the source for our computed values. We'll create first name and last name fields.

💡 Tip:

These are the source fields that our computed values will depend on. As users type in these fields, our computed values will automatically update.

Step 3: Creating a Computed Full Name

Now let's create our first computed value! We'll combine the first and last name into a full name that updates automatically.

💡 Tip:

The computedValue property in the control options creates a reactive value that automatically recalculates when its dependencies change. Try typing in the name fields and watch the full name update in real-time!

Step 4: Real-time Character Counter

Let's add a textarea and create a computed character counter that updates as the user types. This demonstrates how computed values can perform calculations.

💡 Tip:

The character counter uses .length to count characters. The computedValue property automatically updates the display as you type in the bio field!

Step 5: Advanced Computed Values

Finally, let's add a word counter that demonstrates more complex computed value logic. This shows how you can perform sophisticated calculations.

💡 Tip:

The word counter uses string manipulation to split text and count words. The computedValue property can contain any JavaScript logic you need!

Try It Yourself

Challenge 1: Add a computed value that shows the total length of both first and last name combined
Challenge 2: Create a computed value that shows "Hello, [Full Name]!" when both names are entered
Challenge 3: Add a computed value that counts the number of sentences in the bio (split by periods)

Next Steps

Excellent! You've learned the basics of computed values and reactive form behavior. Ready to explore more advanced dynamic features?

Continue to Basic Calculations Tutorial

Other learning paths:

Learn about conditional field visibility
Master form validation with computed values
Create complex multi-step forms