Handling form submissions in modern web applications is crucial for providing users with a responsive and clear experience. In this article, we’ll build a contact form in a React / Next.js project. We use Supabase for backend operations, but this can be adapted to any datasource of course. Our form will display a loading state during submission to prevent multiple submissions, and reset the form after a successful submission.

Check out the GitHub repository here and see the live deployment on Vercel.

Key Features:

1. Displays a "Submitting..." message while processing.
2. Prevents multiple submissions.
3. Updates the UI with a success message once the form is submitted.

Let’s break this down into simple and reusable code examples.

Setting Up the Contact Form

We’ll start by creating the form that users will fill out. In this example, we’re using the useFormState and useFormStatus hooks from React to handle form state and submission status. Here’s the code for the form:

jsxCopy
"use client";

import React from "react";
import { useFormState } from "react-dom";
import { useFormStatus } from "react-dom";
import { sendContactMessage } from "./actions";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Textarea } from "@/components/ui/textarea";
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from "@/components/ui/select";

// Initialize form state
const initialState = {
  message: "",
};

function SubmitButton() {
  const { pending } = useFormStatus(); // Track form submission status
  return (
    <Button
      aria-disabled={pending}
      disabled={pending}
      type="submit"
      className="text-lg outline"
    >
      {pending ? "Submitting..." : "Submit"}
    </Button>
  );
}

export default function ContactForm() {
  const [state, formAction] = useFormState(sendContactMessage, initialState);
  const [selectedType, setSelectedType] =
    (React.useState < string) | (undefined > undefined);

  // Create a ref for the form element
  const formRef = React.useRef < HTMLFormElement > null;

  // Reset the form upon successful submission
  React.useEffect(() => {
    if (state?.message === "Your message has been sent successfully.") {
      if (formRef.current) {
        formRef.current.reset(); // Reset form fields
      }
      setSelectedType(undefined); // Reset the Select component
      alert(state.message); // Optional alert
    }
  }, [state?.message]);

  return (
    <form action={formAction} ref={formRef}>
      <label htmlFor="type">Message Type</label>
      <Select
        name="type"
        required
        value={selectedType}
        onValueChange={setSelectedType}
      >
        <SelectTrigger className="w-[180px]">
          <SelectValue placeholder="Select Type" />
        </SelectTrigger>
        <SelectContent>
          <SelectItem value="correspondence">Correspondence</SelectItem>
          <SelectItem value="bug report">Bug Report</SelectItem>
          <SelectItem value="inquiry">Inquiry</SelectItem>
        </SelectContent>
      </Select>

      <label htmlFor="name">Name</label>
      <Input type="text" id="name" name="name" required />

      <label htmlFor="email">Email</label>
      <Input type="text" id="email" name="email" required />

      <label htmlFor="message">Message</label>
      <Textarea id="message" name="message" required />

      <div className="pt-2">
        <SubmitButton />
      </div>

      <p aria-live="polite" className="sr-only" role="status">
        {state?.message}
      </p>
    </form>
  );
}

Explanation:

• useFormState: Initializes and manages the form’s state. It triggers the sendContactMessage action when the form is submitted.
• useFormStatus: Tracks the submission status, allowing us to display "Submitting..." and disable the button while the form is being processed.
• SubmitButton Component: Handles the button state and updates its label based on the submission status.

Handling the Form Submission

Now let’s implement the sendContactMessage action, which submits the form data to Supabase (or any backend of your choice). This example saves the contact message in a Supabase table called contact_test_app.

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"use server";

import { revalidatePath } from "next/cache";
import { z } from "zod";
import { createClient } from "@/lib/supabase/supabase-client-server";
import { redirect } from "next/navigation";

export async function sendContactMessage(
  state: { message: string },
  formData: FormData
) {
  const supabase = createClient();

  // Define schema for validation
  const schema = z.object({
    name: z.string(),
    email: z.string().email(),
    message: z.string(),
    type: z.string(),
  });

  // Parse and validate the form data
  const data = schema.parse({
    name: formData.get("name"),
    email: formData.get("email"),
    message: formData.get("message"),
    type: formData.get("type"),
  });

  // Simulate an async task
  await new Promise((resolve) => setTimeout(resolve, 500));

  // Insert data into Supabase
  const { error } = await supabase.from("contact_test_app").insert([
    {
      name: data.name,
      email: data.email,
      message: data.message,
      type: data.type,
      created_at: new Date(), // Optional timestamp
    },
  ]);

  if (error) {
    console.error("Error inserting data:", error);
    return {
      message: "An error occurred while sending your message.",
    };
  }

  // Revalidate the page and redirect to a thank you page
  revalidatePath("/contact");
  redirect("/contact/thank-you");

  return {
    message: "Your message has been sent successfully.",
  };
}

Explanation:

• Data Validation: Using zod, we validate the input to ensure that all fields are present and formatted correctly.
• Supabase Integration: We insert the validated data into Supabase. If any errors occur during insertion, we return an error message.
• Revalidate and Redirect: After the data is inserted, we revalidate the page and redirect the user to a thank-you page.

Rendering the Form on the Page

Now, let’s render the contact form on a page. This component wraps our form and is the main entry point.

jsxCopy
import ContactForm from "./form";

export default async function Home() {
  return (
    <div className="grid grid-rows-[20px_1fr_20px] items-center justify-items-center min-h-screen p-8 pb-20 gap-16 sm:p-20 font-[family-name:var(--font-geist-sans)]">
      <main className="flex flex-col gap-8 row-start-2 items-center sm:items-start">
        <ContactForm />
      </main>
    </div>
  );
}

This component sets up a simple grid layout and loads the ContactForm component.

Conclusion

Using Next.js, React, and Supabase, we’ve built a fully functional contact form that handles user input, processes the data, and provides real-time feedback to the user during submission. The form is flexible and can be easily adapted to other data sources or platforms.

Check out the GitHub repository and the live deployment to see this contact form in action.