A simple React component to show how to add a time-delayed typing indicator for a textarea.

IsTyping.js

import React, { Component } from 'react';

class IsTyping extends Component {
  constructor() {
    super();
    this.state = {
      typing: false,
    };
    this.timeout = null;
    this.onChange = this.onChange.bind(this);
  }

  onChange() {
    this.setState({ typing: true });

    // cancel previous timeout if it exists
    if (this.timeout) {
      clearTimeout(this.timeout);
    }

    // set typing to false after one second
    this.timeout = setTimeout(() => {
      this.setState({ typing: false });
    }, 1000);
  }

  render() {
    return (
      <div>
        <textarea name="" id="" cols="30" rows="10" onChange={this.onChange}>
        </textarea>
        {this.state.typing ? <div>Typing...</div> : null}
      </div>
    );
  }
}

export default IsTyping;