react-egghead.io/Lesson15_Validate.html at master · adamsimonini/react-egghead.io · GitHub

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<head>
    <script src="https://unpkg.com/react@16/umd/react.production.min.js"></script>
    <script src="https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.26.0/babel.min.js"></script>
    <link href="https://fonts.googleapis.com/css?family=Roboto+Slab" rel="stylesheet">
    <link rel="icon" href="images/checked.png" type="image/gif" sizes="16x16">
</head>

<style>
    body{
        height: 100vh;

    }
    #root{
        display: flex;
        flex-direction: column;
        justify-content: space-around;
        align-items: center;
        color: black;
        background: url('images/desktop.jpg') no-repeat;
        background-size: 100% 100vh;
        font-family: 'Roboto Slab', serif;
    }
    .title{
        font-size: calc(35px + 1vw);
    }
    .mainDiv{
        display: flex;
        flex-direction: column;
        justify-content: space-around;
        align-items: center;
        height: 50vh;
    }
    form{
        max-width: 70%;
    }
    input{
        max-width: 70%;
        align-self: center;
    }
    button{
        align-self: center;
        text-align: center;
        border-radius: 10px;
        color: black;
        padding: 10px;
        min-width: 100px;
        max-width: 70%;
        font-family: 'Roboto Slab', serif;
        font-size: 30px */
    }
    label{
        font-size: 20px;
    }
    h1{
        font-size: 30px;
    }
    form{
        text-align: center;
        display: flex;
        flex-direction: column;
        justify-content: space-around;
        align-content: center;
        min-height: 40vh;
    }
</style>

<body id="root"></body>

<script type="text/babel">
class NameForm extends React.Component{
    state = {error: null};
    handleSubmit = (e) => {
        e.preventDefault();
        const value = event.target.elements.username.value;
        const error = this.props.getErrorMessage(value);

        if(error){
            alert(`error: ${error}`);
        }else{
            alert(`success: ${value}`);
        }
    }

    handleChange = e => {
        const {value} = e.target;
        this.setState({
            error: this.props.getErrorMessage(value)
        })
    }

    componentDidMount(){
        this.setState({
            error: this.props.getErrorMessage(''),
        })
    }

    render (){
        const {error} = this.state;
        return (
            <form onSubmit={this.handleSubmit}>
                <h1>React Front-End Validation</h1>
                <label>
                    Name:
                </label>
                {error ? <div style={{color: 'red'}}>{error}</div> : null}
                    <input
                        type="text"
                        onChange={this.handleChange}
                        name="username"
                        ref={node => (this.inputNode = node)}
                        />
                    <button
                        disabled={Boolean(error)}
                        type="submit">Submit</button>
            </form>
        )
    }
}

ReactDOM.render(
    <NameForm
        getErrorMessage={value => {
            if(value.length < 3){
                return "Name must be at least 3 characters long";
            }
            if (!value.includes('p')){
                return 'Name must include "p"';
            }
            return null;
        }}
    />,
    document.getElementById('root')
)

</script>