counter_call.js

import React, { Component } from 'react';
import {connection} from './interface/connection'

export default class App extends React.Component {
  state = {
    counter: 0
  }

  componentDidMount() {
    connection.connect("ws://localhost:8500")
  }

  handleAddCall = async () => {
    const result = await connection.call("add", 1)
    this.setState({counter: result})
  }
  
  handleSubstractCall = async () => {
    const result = await connection.call("substract", 1)
    this.setState({counter: result})
  }

  render() {
    return ( 
      <div>
        <button onClick={this.handleAddCall}>+</button>
        <h3>{this.state.counter}</h3>
        <button onClick={this.handleSubstractCall}>-</button>
      </div>
    )
  }

}