title: How to disable form submit button until all input fields are filled?! ReactJS ES2015
body: <p>Hi i found an answer to this for a single field form... but what if we have a form with multiple field? </p>
  
  <p>this is fine for disabling it if you have 1 field but it does not work when you want to disable it based on many fields:</p>
  
  <pre><code>getInitialState() {
      return {email: ''}
    },
    handleChange(e) {
      this.setState({email: e.target.value})
    },
    render() {
      return &lt;div&gt;
        &lt;input name="email" value={this.state.email} onChange={this.handleChange}/&gt;
        &lt;button type="button" disabled={!this.state.email}&gt;Button&lt;/button&gt;
      &lt;/div&gt;
    }
  })
  </code></pre>