[minitech]

> How can I do this without defining a function?

You do define a function, but only once. Constructor:

  this.smth = this.smth.bind(this);

JSX:

  <button onClick={this.smth}></button>

Kind of awkward, but the standard practice last I checked. Arrow methods (terminology?) are also something you can add to the language that does the equivalent of .bind() replacements.