[javascript] Typescript: React event types

What is the correct type for React events. Initially I just used any for the sake of simplicity. Now, I am trying to clean things up and avoid use of any completely.

So in a simple form like this:

export interface LoginProps {
  login: {
    [k: string]: string | Function
    uname: string
    passw: string
    logIn: Function
  }
}
@inject('login') @observer
export class Login extends Component<LoginProps, {}> {
  update = (e: React.SyntheticEvent<EventTarget>): void => {
    this.props.login[e.target.name] = e.target.value
  }
  submit = (e: any): void => {
    this.props.login.logIn()
    e.preventDefault()
  }
  render() {
    const { uname, passw } = this.props.login
    return (
      <div id='login' >
        <form>
          <input
            placeholder='Username'
            type="text"
            name='uname'
            value={uname}
            onChange={this.update}
          />
          <input
            placeholder='Password'
            type="password"
            name='passw'
            value={passw}
            onChange={this.update}
          />
          <button type="submit" onClick={this.submit} >
            Submit
          </button>
        </form>
      </div>
    )
  }
}

What type do I use here as event type?

React.SyntheticEvent<EventTarget> does not seem to be working as I get an error that name and value do not exist on target.

More generalised answer for all events would be really appreciated.

Thanks

I think the simplest way is that:

type InputEvent = React.ChangeEvent<HTMLInputElement>;
type ButtonEvent = React.MouseEvent<HTMLButtonElement>;

update = (e: InputEvent): void => this.props.login[e.target.name] = e.target.value;
submit = (e:  ButtonEvent): void => {
    this.props.login.logIn();
    e.preventDefault();
}

you can do like this in react

handleEvent = (e: React.SyntheticEvent<EventTarget>) => {
  const simpleInput = (e.target as HTMLInputElement).value;
  //for simple html input values
  const formInput = (e.target as HTMLFormElement).files[0];
  //for html form elements
}

To combine both Nitzan's and Edwin's answers, I found that something like this works for me:

update = (e: React.FormEvent<EventTarget>): void => {
    let target = e.target as HTMLInputElement;
    this.props.login[target.name] = target.value;
}

For those who are looking for a solution to get an event and store something, in my case a HTML 5 element, on a useState here's my solution:

const [anchorElement, setAnchorElement] = useState<HTMLButtonElement | null>(null);

const handleMenu = (event: React.MouseEvent<HTMLButtonElement, MouseEvent>) : void => {
    setAnchorElement(event.currentTarget);
};

for update: event: React.ChangeEvent for submit: event: React.FormEvent for click: event: React.MouseEvent

I have the following in a types.ts file for html input, select, and textarea:

export type InputChangeEventHandler = React.ChangeEventHandler<HTMLInputElement>
export type TextareaChangeEventHandler = React.ChangeEventHandler<HTMLTextAreaElement>
export type SelectChangeEventHandler = React.ChangeEventHandler<HTMLSelectElement>

Then import them:

import { InputChangeEventHandler } from '../types'

Then use them:

const updateName: InputChangeEventHandler = (event) => {
  // Do something with `event.currentTarget.value`
}
const updateBio: TextareaChangeEventHandler = (event) => {
  // Do something with `event.currentTarget.value`
}
const updateSize: SelectChangeEventHandler = (event) => {
  // Do something with `event.currentTarget.value`
}

Then apply the functions on your markup (replacing ... with other necessary props):

<input onChange={updateName} ... />
<textarea onChange={updateName} ... />
<select onChange={updateSize} ... >
  // ...
</select>

The problem is not with the Event type, but that the EventTarget interface in typescript only has 3 methods:

interface EventTarget {
    addEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
    dispatchEvent(evt: Event): boolean;
    removeEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
}

interface SyntheticEvent {
    bubbles: boolean;
    cancelable: boolean;
    currentTarget: EventTarget;
    defaultPrevented: boolean;
    eventPhase: number;
    isTrusted: boolean;
    nativeEvent: Event;
    preventDefault(): void;
    stopPropagation(): void;
    target: EventTarget;
    timeStamp: Date;
    type: string;
}

So it is correct that name and value don't exist on EventTarget. What you need to do is to cast the target to the specific element type with the properties you need. In this case it will be HTMLInputElement.

update = (e: React.SyntheticEvent): void => {
    let target = e.target as HTMLInputElement;
    this.props.login[target.name] = target.value;
}

Also for events instead of React.SyntheticEvent, you can also type them as following: Event, MouseEvent, KeyboardEvent...etc, depends on the use case of the handler.

The best way to see all these type definitions is to checkout the .d.ts files from both typescript & react.

Also check out the following link for more explanations: Why is Event.target not Element in Typescript?