I'm having problems sending the form in ReactJS, I get the following error "Can not Post", does anyone know why?

import React, {Component} from 'react';
import './Calcular.css';

class Calcular extends Component{

    state = {
        number1: '',
        number2: '',
        type: '',
        result: ''
    }

    Calc = () => {
        switch(this.state.type){
            case 'plus':
                this.setState({ result: parseInt(this.state.number1) + parseInt(this.state.number2) });
                break;
            case 'minus':
                this.setState({ result: this.state.number1 - this.state.number2 });
                break;
            case 'mult':
                this.setState({ result: this.state.number1 * this.state.number2 });
                break;
            case 'div':
                this.setState({ result: this.state.number1 / this.state.number2 });
                break;
            default:
                break;
        }
    }

    onSubmitInput = (e) => {
        this.setState({ "number1": e.target[0].value, "number2": e.target[1].value, "type": e.target.types.value});
        this.Calc();         
    }

    render(){
        return(
            <div>
                <form className="div-calc" onSubmit={this.onSubmitInput.bind(this)} method="post" >
                    <input type="number" name="number1" placeholder="Number 1" />
                    <input type="number" name="number2" placeholder="Number 2" />
                    <select name="types">
                        <option>Operação: </option>
                        <option value="plus"> Somar </option>
                        <option value="minus"> Subtrair </option>
                        <option value="mult"> Multiplicar </option>
                        <option value="div" > Dividir </option>
                    </select>
                    <button type="submit" > Calcular </button>
                </form>
                <h3>O resultado é: {this.state.result}</h3>
            </div>
        );  
    }

}

export default Calcular;