Hamid

Posted on Sep 8, 2021 • Edited on May 11 • Originally published at hamidmehmood.vercel.app

Simple way to write forms in React with Formik

#react #javascript #css #tutorial

Formik is a best library and I use it every time. So today I am writing this post for fundamentals of formik and it covers the use of formik in simple way .

Create and style a login form

I created login form like this

 <form className="form">
        <div className="field">
          <label htmlFor="email">Email Address</label>
          <input
            id="email"
            name="email"
            type="email"
            placeholder="email"
          />
        </div>
        <div className="field">

          <input
            id="password"
            name="password"
            type="password"
            placeholder="password"
          />
        </div>
        <button type="submit" className="submit-btn">
          Login
        </button>
      </form>

and styled it like this

.App {
  font-family: sans-serif;
  text-align: center;
  display: grid;
  place-items: center;
}
.form {
  width: 300px;
  display: grid;
  gap: 10px 0px;
  margin-top: 50px;
  background-color: #ddd;
  border-radius: 8px;
  padding: 10px;
}
.field {
  display: flex;
  justify-content: space-between;
  padding-bottom: 10px;
}
.submit-btn {
  width: 80px;
}
.error {
  color: red;
  font-size: 12px;
  justify-self: start;
  font-style: italic;
  padding-bottom: 10px;
  line-height: 3px;
}

After this, you'll get a login form same as this

Initialize formik default states

Lets import the useFormik first from the formik.

import { useFormik } from "formik";

Now you can initialize the initialValues of form using useFormik hook .

const formik = useFormik({
    initialValues: {
      email: "",
      password: ""
    },
)}

let's apply formik to our input fields .

   ...
          <input
            id="email"
            name="email"
            type="email"
            placeholder="email"
            onChange={formik.handleChange}
            onBlur={formik.handleBlur}
            value={formik.values.email}
          />
     ...
          <input
            id="password"
            name="password"
            type="password"
            placeholder="password"
            onChange={formik.handleChange}
            onBlur={formik.handleBlur}
            value={formik.values.password}
          />

Apply validations on login fields

I used Yup library to apply validations on my fields
So first import Yup like this .

import * as Yup from "yup";

Then I added validationSchema for my login fields

const validationSchema = yup.object({
    email: yup
      .string()
      .email('Please enter a valid email address')
      .required('Email is required'),
    password: yup
      .string()
      .min(8, 'Please enter strong password')
      .required('Password is required'),
  })
  const formik = useFormik({
    initialValues: {
      email: "",
      password: ""
    },
    validationSchema,
)};

Here Yup is validating if the values of the field are provided; if yes, then is it correct format or not.
So if any error happens according to our validation schema, it will be stored in formik's errors object and we can print it beside or below the field like this .

{formik.touched.email && formik.errors.email ? (
         <span className="error">{formik.errors.email}</span>
) : null}

Now our form looks like this with validation errors

Write submit form function

The last step is to create submit function and perform your operation on formik values. You can navigate to the next screen, call API, or anything you want to do. I just set a state on submit and shown a message to a user on the login .

const formik = useFormik({
    initialValues: {
      email: "",
      password: ""
    },
    validationSchema,
    onSubmit: (values) => {
      setIsLoggedIn(true);
    }
  });

and pass formik handleSubmit function to your form like this

<form className="form" onSubmit={formik.handleSubmit}>

and here your form is ready with field validations!!
You can find the full source code here

https://codesandbox.io/s/unruffled-tharp-uti1k?file=/src/App.js:727-781

Top comments (10)

Victor Ocnarescu • Sep 9 '21 • Edited

Formik is indeed awesome. Have you ever tried Formik Fields? They automatically bind onChange, onBlur and value to your input (and you don't have to declare them all the time).

Without Formik Fields:

<input
  id="password"
  name="password"
  type="password"
  placeholder="password"
  onChange={formik.handleChange}
  onBlur={formik.handleBlur}
  value={formik.values.password}
/>

With Formik Fields:

<Field
  id="password"
  name="password"
  type="password"
  as="input"
/>

Hamid • Sep 9 '21

Incredible I will give it try sir .

Victor Ocnarescu • Sep 9 '21

I respectfully disagree. How about touched fields handling? Or error messages and states? Submit count for your forms? Even validation that is not your basic HTML5 validation? These are all handled by Formik by default and you don't have to worry about them.

My forms have become really clean after I started using this library. I cannot recommend Formik enough.

Victor Ocnarescu • Sep 9 '21

The drawback to using "basic" form logic instead of a specific package like Formik is it can get complicated along the way. And most of the times it does get more complicated.

Imagine you start a simple login form, everything is great. Basic HTML5 validation works. Then your client comes up and wants to display an error message tied to the username field, only when the form was already submitted and the username does not exist (check the login on Netflix for this exact scenario).

Now here is the part it gets messy. You don't exactly know what to do. Should you implement these yourself? Or maybe a package like Formik? It did not get too complicated, it's still a form with 2 fields: username and password.

Of course, you are right about the HTML5 validation. You can get that for free in every browser and it improves UX. But Formik (or a similar package that improves forms) is the next best thing. Forms get messier and messier as your projects evolve.