How to get form data from input fields in React

Question

The constructor and function:

constructor(props) {
    super(props);

    this.state = {
        tagline: 'We rank what people are talking about.',
        year: new Date().getFullYear()
    };

    this.onFormSubmit = this.onFormSubmit.bind(this);
}

onFormSubmit(e) {
    console.log('onFormSubmit', e)
    console.log('this.state', this.state);
};

The form (classNames removed for clarity):

<form onSubmit={ this.onFormSubmit }>
    <div className="fl w100">
        <div>
            <input type="text" id="email" value={ this.state.email }/>
            <label htmlFor="email">Email</label>
        </div>
    </div>

    <div className="fl w100">
        <div>
            <input type="password" id="password" value={ this.state.password }/>
            <label htmlFor="password">Password</label>
        </div>
    </div>

    <button type="submit">
        Login
    </button>
</form>

This is what logs out, note no email or password information:

Full Login component code

---

import React from 'react';

class Login extends React.Component {

    constructor(props) {
        super(props);

        this.state = {
            tagline: 'We rank what people are talking about.',
            year: new Date().getFullYear()
        };

        this.onFormSubmit = this.onFormSubmit.bind(this);
    }

    onFormSubmit(e) {
        console.log('onFormSubmit', e)
        console.log('this.state', this.state);
    };

    render() {
        return (<div className="app">
            <div className="welcome">
                <header>
                    <div className="wikitags-logo">
                        <img src="imgs/wikitags-logo.png"/>
                    </div>
                    <h2>Admin Portal</h2>
                    <p>{ this.state.tagline }</p>
                </header>

                <section className="login-form">
                    <form onSubmit={ this.onFormSubmit }>
                        <div className="fl w100">
                            <div className="mdl-textfield mdl-js-textfield">
                                <input className="mdl-textfield__input" type="text" id="email" value={ this.state.email }/>
                                <label className="mdl-textfield__label" htmlFor="email">Email</label>
                            </div>
                        </div>

                        <div className="fl w100">
                            <div className="mdl-textfield mdl-js-textfield">
                                <input className="mdl-textfield__input" type="password" id="password" value={ this.state.password }/>
                                <label className="mdl-textfield__label" htmlFor="password">Password</label>
                            </div>
                        </div>

                        <button type="submit" className="mdl-button mdl-js-button mdl-button--raised mdl-js-ripple-effect mdl-button--accent">
                            Login
                        </button>
                    </form>
                </section>

                <footer>
                    &copy; { this.state.year } WikiTags
                </footer>
            </div>
        </div>);
    }
}

export default Login;

Answer 1

Suggestions:

1. You are using value property with input fields but you didn't defined the onChange method so your input fields will be read-only because state value will not get updated.

2. You need to define a onChange event will all the input fields or make them uncontrolled element by removing the value property.

3. In case of uncontrolled element define the ref to each field and to access the value use this.ref_name.value.

By Defining the onChange event:

Define the name property to each input element (name should be same as state variable name it will help to update the state and we can handle all the change in single onChange function) like this:

<input type="text" name='value' value={this.state.value} onChange={(e) => this.handleChange(e)} />

handleChange(e){
   this.setState({[e.target.name]: e.target.value})
}

By Uncotrolled element:

<input type="text" ref={el => this.el = el} />

Now inside onSubmit function use this.el.value to access he values of this input field.

Check this answer for reference: https://stackoverflow.com/a/43695213/5185595