Formik is a super cool library and I use it every time. So today I am writing this post for beginners and it covers the use of formik on the simple login form.

I'll cover these things here

Create and style a basic login form
Initialize formik default states
Apply validation on login fields
Write submit form function

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"
          />
        </div>
        <div className="field">
          <label htmlFor="password">Password</label>
          <input
            id="password"
            name="password"
            type="password"
          />
        </div>
        <button type="submit" className="submit-btn">
          Login
        </button>
      </form>

and styled it like this

.form {
  width: 300px;
  display: flex;
  flex-direction: column;
  margin-top: 50px;
  background-color: #ddd;
  border-radius: 8px;
  padding: 10px;
}
.field {
  display: flex;
  justify-content: space-between;
  padding-bottom: 10px;
}
.submit-btn {
  align-self: flex-end;
  width: 80px;
}

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 create a formik object using useFormik hook and define your initialValues in it

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

let's use the formik handleChange function and pass formik values to our input fields

     ...
          <input
            id="email"
            name="email"
            type="email"
            onChange={formik.handleChange}
            onBlur={formik.handleBlur}
            value={formik.values.email}
          />
     ...
          <input
            id="password"
            name="password"
            type="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. You can use custom regex as well if you don't want to use Yup for some reason.
So first import Yup like this

import * as Yup from "yup";

Then I added validationSchema for my login fields

 const formik = useFormik({
    initialValues: {
      email: "",
      password: ""
    },
    validationSchema: Yup.object().shape({
      email: Yup.string()
        .email("Invalid email address")
        .required("Please enter email"),
      password: Yup.string().required("Please enter password")
    }),
  });

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: Yup.object().shape({
      email: Yup.string()
        .email("Invalid email address")
        .required("Please enter email"),
      password: Yup.string().required("Please enter password")
    }),
    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

How to use formik with useFormik prop in react

Create and style a login form

Initialize formik default states

Apply validations on login fields

Write submit form function