Spinner

Component.js

class Component {
    render() {
        return this.renderWithTemplate(this.state);
    }
    
    initializeEvent(element, name, expession) {
        element.addEventListener(name, generateEventHandler(this[name], expression), false)
    }
}

spec.js

let spinner = new Spinner({value: 1, step: 2});
spinner.increment(); // Error: Not rendered
spinner.render();

spinner.increment();
expect(spinner.state.value).toBe(3):

spinner.increment(); // Not stateless
expect(spinner.state.value).toBe(5):

Spinner.js

class Spinner extends Component {
    tempalte = '<input /><span on-click="increment">UP</span><span on-click="decrement">DOWN</span>'
    
    increment() {
        this.setState({value: this.state.value + this.state.step})
    }
    
    decrement() {
        this.setState({value: this.state.value - this.state.step})
    }
}