First argument in update method is SyntheticEvent object that contains common properties and methods to any event, it is not reference to React component where there is property props.
if you need pass argument to update method you can do it like this
onClick={ (e) => this.props.onClick(e, 'home', 'Home') }
and get these arguments inside update method
update(e, space, txt){
console.log(e.target, space, txt);
}
event.target gives you the native DOMNode, then you need to use the regular DOM APIs to access attributes. For instance getAttribute or dataset
<button
data-space="home"
className="home"
data-txt="Home"
onClick={ this.props.onClick }
/>
Button
</button>
onClick(e) {
console.log(e.target.dataset.txt, e.target.dataset.space);
}