React TypeError this._test is not a function

Question

Since im new to JavaScript and React, i really have problems figuring out the right syntax.

Here my problem:

_handleDrop(files) should call the

Answer 1

The way we solved this issue is to use an experimental es7 feature which lets you declare a function in this way within a class:

handleExpandCollapse = () => {
    this.setState({
      isExpanded: !this.state.isExpanded,
    });
  }

And that is autobound to this, so your JSX will be the same.