Basic React form submit refreshes entire page

Just call event.preventDefault method to prevent default behavior of form

afterSubmission(event) {
    event.preventDefault();
    let name = this.state.itemName;
    this.setState ({
        storedItemName:this.state.itemName
    }, function() {
        alert(this.state.storedItemName); // Shows the right value!
    }
}

To prevent basic React form submit from refreshing the entire page, we call e.preventDefault. in the submit event handler.

For instance, we write:

import React from "react";

export default function App() {
  const onSubmit = (e) => {
    e.preventDefault();
    console.log("refresh prevented");
  };

  return (
    <div>
      <form onSubmit={onSubmit}>
        <button type="submit">submit</button>
      </form>
    </div>
  );
}

to create the onSubmit function that’s set as the value of the onSubmit prop.

In the function, we call e.preventDefault to prevent the default submission behavior, which is to do server side form submission which refreshes the whole page.

We have a submit button in the form to do the form submission.

Therefore, instead of seeing the page refresh when we click submit, we should see the 'refresh prevented' string logged in the console instead.

There are 3 ways you can do this:

1st WAY

By using event.preventDefault(); function

• When we use onSubmit() event for form submission the default behaviour of this event is to refresh the browser and render a new html page.
• To prevent this default behaviour of page refresh for onSubmit event we put event.preventDefault(); inside the function we are calling for onSubmit event.

InputField.js

class InputField extends React.Component {
    
        state = {
                  itemName: "",
                  storedItemName: "",
                }
    
        handleNameChange = (event) => { 
            const { name,value } = event.target;  
            //we can't write this.setState({name:value}) this will set name as the key we need value of the name which is itemName
            
            this.setState({
                [name] : value //itemName:"the text we will enter" 
            });
        }
        afterSubmission = (event) => {
            event.preventDefault();
            this.setState ({
                storedItemName:this.state.itemName
            }, function() {
                alert(this.state.storedItemName);
            });
        }
        render() {
            return(
                <div>
                    <form onSubmit = {this.afterSubmission}>
                        <label> Item Name: 
                        <input 
                            onChange = {this.handleNameChange}
                            type = "text" 
                            name = "itemName" 
                            value = {this.state.itemName} 
                        />
                        </label>                    
                        <input type = "submit" value = "Submit" />
                    </form>
                    <div className = "itemList">
                        <p>Hi</p>
                        {this.state.storedItemName}
                    </div>
                </div>
            );
        }
    }
    
    export default InputField;

2nd WAY

• By removing onSubmit event from form element

• Next is change the input type of submit to input type button and add an onClick event to it

InputField.js

class InputField extends React.Component {

    state = {
              itemName: "",
              storedItemName: "",
            }

    handleNameChange = (event) => { 
        console.log(this);    
        const { name,value } = event.target;  
        this.setState({
            [name] : value
        });
    }
    afterSubmission = () => {
        this.setState ({
            storedItemName:this.state.itemName
        }, function() {
            alert(this.state.storedItemName);
        });
    }
    render() {
        return(
            <div>
                <form>
                    <label> Item Name: 
                    <input 
                        onChange = {this.handleNameChange}
                        type = "text" 
                        name = "itemName" 
                        value = {this.state.itemName} 
                    />
                    </label>                    
                    <input 
                        type = "button" 
                        onClick={this.afterSubmission} 
                        value = "Submit" 
                    />
                </form>
                <div className = "itemList">
                    <p>Hi</p>
                    {this.state.storedItemName}
                </div>
            </div>
        );
    }
}

export default InputField;

3rd WAY

By using react form hook (https://www.react-hook-form.com/)

• As per docs we have to install the npm module in our development server

npm install react-hook-form

InputField.js

import InputFieldForm from 'location specified';
    class InputField extends React.Component {
            
      render() {
        return(
              <div>
                  <InputFieldForm />
              </div>
              );
       }
    }
    export default InputField;

InputFieldForm.js

import React from "react";
import { useForm } from "react-hook-form";

const InputFieldForm = () =>{
    const onSubmit = (formData) =>{
        alert(JSON.stringify(formData));
        console.log(formData);
    } 

    const { register, handleSubmit } = useForm();
    return(
        <form onSubmit = {handleSubmit(onSubmit)}>
            <label> Item Name: 
            <input 
                {...register('itemName')}
                type = "text" 
                name = "itemName" 
            />
            </label>                    
            <input type = "submit" value = "Submit" />
        </form>
    )
}

export default InputFieldForm;

Prevent the default behaviour:

afterSubmission(event) {
    event.preventDefault();
    let name = this.state.itemName;
    this.setState ({
        storedItemName:this.state.itemName
    }, function() {
        alert(this.state.storedItemName); // Shows the right value!
    });
}