Reagovať onchange vstup

Príklady kódu

forma v Reacte

import React, { useState } from "react";
import "./styles.css";
function Form() {
  const [firstName, setFirstName] = useState("");
  const [lastName, setLastName] = useState("");
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");
  return (
    <form>
      <input
        value={firstName}
        onChange={e => setFirstName(e.target.value)}
        placeholder="First name"
        type="text"
        name="firstName"
        required
      />
      <input
        value={lastName}
        onChange={e => setLastName(e.target.value)}
        placeholder="Last name"
        type="text"
        name="lastName"
        required
      />
      <input
        value={email}
        onChange={e => setEmail(e.target.value)}
        placeholder="Email address"
        type="email"
        name="email"
        required
      />
      <input
        value={password}
        onChange={e => setPassword(e.target.value)}
        placeholder="Password"
        type="password"
        name="password"
        required
      />
      <button type="submit">Submit</button>
    </form>
  );
}
export default Form;

reagovať zadávanie textu onchange

class NameForm extends React.Component {
  constructor(props) {
    super(props);
    this.state = {value: ''};
    this.handleChange = this.handleChange.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleChange(event) {    this.setState({value: event.target.value});  }
  handleSubmit(event) {
    alert('A name was submitted: ' + this.state.value);
    event.preventDefault();
  }

  render() {
    return (
      <form onSubmit={this.handleSubmit}>
        <label>
          Name:
          <input type="text" value={this.state.value} onChange={this.handleChange} />        </label>
        <input type="submit" value="Submit" />
      </form>
    );
  }
}

html vybrať reagovať

class FlavorForm extends React.Component {
  constructor(props) {
    super(props);
    this.state = {value: 'coconut'};
    this.handleChange = this.handleChange.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleChange(event) {    this.setState({value: event.target.value});  }
  handleSubmit(event) {
    alert('Your favorite flavor is: ' + this.state.value);
    event.preventDefault();
  }

  render() {
    return (
      <form onSubmit={this.handleSubmit}>
        <label>
          Pick your favorite flavor:
          <select value={this.state.value} onChange={this.handleChange}>            <option value="grapefruit">Grapefruit</option>
            <option value="lime">Lime</option>
            <option value="coconut">Coconut</option>
            <option value="mango">Mango</option>
          </select>
        </label>
        <input type="submit" value="Submit" />
      </form>
    );
  }
}

reagovať ako odovzdať vstupnú cieľovú hodnotu

class NameForm extends React.Component {
  constructor(props) {
    super(props);
    this.state = {value: ''};

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

  handleChange(event) {
    this.setState({value: event.target.value});
  }

  render() {
    return (
      <form>
        <label>
          Name:
          <input type="text" value={this.state.value} onChange={this.handleChange} />
        </label>
        <input type="submit" value="Submit" />
      </form>
    );
  }
}

rukoväť onchange reagovať

import React, { Component } from 'react';

import './App.css';
import Header from './Header';

class App extends Component {

  constructor(props) {
    super(props);
   this.state = {name: "Michael"}

  }
   changeTitle = (e) =>{
      this.setState({name: e.target.value});
    }

  render() {
    return (
      <div className="App">
        <Header title={this.state.name}/>
        <p className="App-intro">
          Type here to change name.
        <input type="text" onChange={this.changeTitle}/>
        </p>
      </div>
    );
  }
}

export default App;

čo robí onchange v Reacte

In React, onChange is used to handle user input in real-time.

If you want to build a form in React, you need to use this event to track 
the value of input elements.