somebody knows how could I extract plain text from a react component?

example:

```
const reactObject = 
  <div className="text-primary">
    <span>this is a react object, </span>
    <b>builded with jsx!!!!</b>
  </div>;
.....
//what should I do inside extractText????
const plainText = extractText(reactObject);
alert(reactObject);//result: "[Object object]"
alert(plainText);// must result: "this is a react object builded with jsx!!!!"

```