index.js

// components/Attribute.js

function Attribute(props) {
	return (
		<div>
			<a onClick={props.onClick}>
				{props.name}
			</a>
		</div>
	);
}

// components/Sheet.js

function Sheet(props) {
	return (
		<div>
			<Attribute name="Strength" value={props.strength} onClick={() => props.onChange('strength')} />
			<Attribute name="Agility" value={props.agility} onClick={() => props.onChange('agility')} />
		</div>
	);
}

// index.js
const char = new Character();

function changeAttribute(attrName) {
	char.changeAttribute(attrName);
	render();
}

function render() {
	ReactDOM.render(<Sheet
		strength={char.strength}
		agility={char.agility}
		onChange={char.changeAttribute}
	/>);
}

render();