React 合成事件与原生 Javascript 事件？

Question

I have a hard time understanding react synthetic events.

The way I debug with native javascript events is something like this

window.addEventListener('mousemove',
  function(event){
    console.log(event);
})

If I move my mouse, and check the console, I can see the events properties such as target and other useful properties such as innerHTML , nextElementSibling , lastChild etc.

I have a simple react app below. Its an input field with a submit button. If something is entered in the input when submitted, an alert pops up. Otherwise nothing

 // React Synthetic Events class AddOption extends React.Component { handleAddOption(e){ e.preventDefault(); console.log(e); const option = e.target.elements.option.value; // < HOW WOULD I FIND THIS IN THE DEBUGGER? if (option){ alert("something was entered in"); } } render() { return ( <div> <form onSubmit={this.handleAddOption}> <input type="text" name="option" /> <button>React Submit</button> </form> </div> ) } } ReactDOM.render(<AddOption />, document.getElementById('app'));

 <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script> <div id="app"><!-- reactapp -->

What I don't get is if I inspect the page it doesn't give that useful information like I get with native events.

The issue is I referenced in my reactapp (following a tutorial) to use e.target.element.options.value . I have no idea how someone would find that out in the debugger. I don't see a reference to anything dubbed element in any of the long nested chain of prototype properties under synthetic event's target . I tried CTRL+F but I don't think chrome supports searching nested prototypes

Am I not understanding something about things happening in the virtual DOM / react in general?

Answer 1

per li357 comment, adding e.persist() right before the console.log(e) statement in original post shows this in the debugger. You can see the native javascript event's properties include target , element and the defined option from react

Answer 2

You can use e.nativeEvent to get access to the native event and from there on to the elements.option.value property:

// React Synthetic Events
class AddOption extends React.Component {
    handleAddOption(e){
      e.preventDefault();
      console.log(e);

      const option = e.target.elements.option.value; // < HOW WOULD I FIND THIS IN THE DEBUGGER?
      // > YOU CAN USE e.nativeEvent TO GET ACCESS TO THE NATIVE EVENT:
      console.log(e.nativeEvent);
      console.log(e.nativeEvent.target.elements.option.value); // < HERE IS YOUR VALUE

      if (option){
        alert("something was entered in");
      }
    }
    render() {
      return (
        <div>
          <form onSubmit={this.handleAddOption}>
            <input type="text" name="option" defaultValue={"Toy"}/>
            <button>React Submit</button>
          </form>
        </div>
      )
    }
}
ReactDOM.render(<AddOption />, document.getElementById('root'));