React

HTML

<div id="app"></div>

React

class TodoApp extends React.Component {
  constructor() {
    super()

    this.state = {
      number: 1
    }

    this.handleInputChange = this.handleInputChange.bind(this)
    this.formatInput = this.formatInput.bind(this)
  }

  handleInputChange(event) {
  	console.log(event.target.value)
    this.setState({
      number: event.target.value
    })
  }
  
  formatInput() {
  	var num = this.state.number
  	this.setState({
    	number: parseFloat(num).toFixed(2)
    })
  }
  
  render() {
    return (
      <div>
        <input
          type="number"
          value={ this.state.number }
          onChange={ this.handleInputChange }
          onBlur={ this.formatInput }
          />
      </div>
    )
  }
}

ReactDOM.render(<TodoApp />, document.querySelector("#app"))