# how to define use and bind

class TotalValue extends Component {
constructor(props) {
super(props);

// Step 3. bind this
this.showSum = this.showSum.bind(this);
}

// Step 1. function define
showSum() {
// total number
}

render () {
return (
<div>
{/* { Step 2. function Use } */}
{this.showSum()}
</div>
)
}
}