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reactjsreact-reduxreact-propsreact-state-managementreact-functional-component

How to solve the React error: Cannot read 'Props' of undefined


I'm trying out to work on integrating a library called react-phone-number-input with my multi-step react form as per the following as a functional component:

import React, { useState } from "react";
import Helmet from "react-helmet";
import "./reg-style/Credentail.css";
import "react-phone-number-input/style.css";
import PhoneInput from "react-phone-number-input";

export default function Credential() {
  const alter = e => {
    e.preventDefault();
    this.props.nextStep();
  };

  const back = e => {
    e.preventDefault();
    this.props.prevStep();
  };

  const [values, handleChange] = this.props;
  const [value, setValue] = useState();
  return (
    <div>
      <Helmet>
        <body className="form-bg-col" />
      </Helmet>

      <div className="login">
        <div className="reg-container">
          <button onClick={back} className="col-form-prev">
            <i class="fa fa-chevron-left" />
          </button>
          <div className="user-detail email">
            Email:
            <input
              onChange={handleChange("Email")}
              defaultValue={values.Email}
              type="email"
              placeholder="Enter your Email"
            />
          </div>
          <div
            className="user-detail"
            onChange={handleChange("Phone")}
            defaultValue={values.Phone}
          >
            Phone:
            <PhoneInput
              displayInitialValueAsLocalNumber
              placeholder="Enter phone number"
              defaultCountry="IN"
              value={value}
              onChange={setValue}
            />
          </div>
          <div className="user-detail username">
            Username:
            <input
              onChange={handleChange("Username")}
              defaultValue={values.Username}
              type="text"
              placeholder="Select your unique Username"
            />
          </div>
          <div className="user-detail password">
            Password:
            <input
              onChange={handleChange("Password")}
              defaultValue={values.Password}
              type="password"
              placeholder="Choose your Password"
            />
          </div>

          <button onClick={alter} className="col-form-next">
            <i class="fa fa-chevron-right" />
          </button>
        </div>
      </div>
    </div>
  );
}

While running it, it throws me an error:

TypeError: Cannot read property 'props' of undefined
Credential
C:/Users/Rahul/Desktop/collegefacemash/src/form/register/Credential.js:78
  75 | import "react-phone-number-input/style.css";
  76 | import PhoneInput from "react-phone-number-input";
  77 | 
> 78 | export default function Credential(props) {
  79 |   const alter = e => {
  80 |     e.preventDefault();
  81 |     this.props.nextStep();

what should i do to make my app work?
This multi step form is inspired from: Multi Step Form With React & Material UI by Traversy Media
Your help will be extremely valueable for me...


Solution

  • On a functional component you don't use the this keyword.

    I changed your code in order to make it work:

    import React, { useState } from "react";
    import Helmet from "react-helmet";
    import "./reg-style/Credentail.css";
    import "react-phone-number-input/style.css";
    import PhoneInput from "react-phone-number-input";
    
    export default function Credential(props) {
      const alter = e => {
        e.preventDefault();
        props.nextStep();
      };
    
      const back = e => {
        e.preventDefault();
        props.prevStep();
      };
    
      const {values, handleChange} = props;
      const [value, setValue] = useState();
      return (
        <div>
          <Helmet>
            <body className="form-bg-col" />
          </Helmet>
    
          <div className="login">
            <div className="reg-container">
              <button onClick={back} className="col-form-prev">
                <i class="fa fa-chevron-left" />
              </button>
              <div className="user-detail email">
                Email:
                <input
                  onChange={handleChange("Email")}
                  defaultValue={values.Email}
                  type="email"
                  placeholder="Enter your Email"
                />
              </div>
              <div
                className="user-detail"
                onChange={handleChange("Phone")}
                defaultValue={values.Phone}
              >
                Phone:
                <PhoneInput
                  displayInitialValueAsLocalNumber
                  placeholder="Enter phone number"
                  defaultCountry="IN"
                  value={value}
                  onChange={setValue}
                />
              </div>
              <div className="user-detail username">
                Username:
                <input
                  onChange={handleChange("Username")}
                  defaultValue={values.Username}
                  type="text"
                  placeholder="Select your unique Username"
                />
              </div>
              <div className="user-detail password">
                Password:
                <input
                  onChange={handleChange("Password")}
                  defaultValue={values.Password}
                  type="password"
                  placeholder="Choose your Password"
                />
              </div>
    
              <button onClick={alter} className="col-form-next">
                <i class="fa fa-chevron-right" />
              </button>
            </div>
          </div>
        </div>
      );
    }
    

    Can you see what I did?

    line 7: added props param
    line 10 & 15: removed "this"
    line 18: removed "this" and changed from [values, handleChange] to {values, handleChange} in order to destructuring your props object