TypeScript interface signature for the onClick event in ReactJS
JavascriptReactjsTypescriptJavascript Problem Overview
The official reactjs.org website contains an excellent introductory tutorial.
The tutorial snippets are written in JavaScript and I am trying to convert these to TypeScript.
I have managed to get the code working but have a question about using interfaces.
What should the correct "function signature" be for the onClick callback.
Is there a way to replace the 'any' keyword in the IProps_Square interface with an explicit function signature ?
Any help or suggestions would be really appreciated, many thanks Russell
index.html
<!DOCTYPE html>
<html lang="en">
<body>
<div id="reactjs-tutorial"></div>
</body>
</html>
index.tsx
import * as React from 'react';
import * as ReactDOM from 'react-dom';
interface IProps_Square {
message: string,
onClick: any,
}
class Square extends React.Component < IProps_Square > {
render() {
return (
<button onClick={this.props.onClick}>
{this.props.message}
</button>
);
}
}
class Game extends React.Component {
render() {
return (
<Square
message = { 'click this' }
onClick = { () => alert('hello') }
/>
);
}
}
ReactDOM.render(
<Game />,
document.getElementById('reactjs-tutorial')
);
Javascript Solutions
Solution 1 - Javascript
The interface with props should be
interface IProps_Square {
message: string;
onClick: React.MouseEventHandler<HTMLButtonElement>;
}
Notice also that if you use semicolons, the interface items separator is a semicolon, not a comma.
Solution 2 - Javascript
> Is there a way to replace the 'any' keyword in the IProps_Square interface with an explicit function signature
I would just () => void i.e. a function that takes no arguments and you don't care if it returns anything.
import * as React from 'react';
import * as ReactDOM from 'react-dom';
interface IProps_Square {
message: string,
onClick: () => void,
}
class Square extends React.Component < IProps_Square > {
render() {
return (
<button onClick={this.props.onClick}>
{this.props.message}
</button>
);
}
}
class Game extends React.Component {
render() {
return (
<Square
message = { 'click this' }
onClick = { () => alert('hello') }
/>
);
}
}
ReactDOM.render(
<Game />,
document.getElementById('reactjs-tutorial')
);
However if you need the parameter the proper type for it is React.MouseEvent<HTMLElement>, so:
interface IProps_Square {
message: string,
onClick: (e: React.MouseEvent<HTMLElement>) => void,
}
Solution 3 - Javascript
Except React.MouseEvent
type IProps_Square = {
onClick: React.ButtonHTMLAttributes<HTMLButtonElement>["onClick"];
}
or
type IProps_Square = {
onClick: JSX.IntrinsicElements["button"]["onClick"];
}
Solution 4 - Javascript
How do you declare the type for handleClick?
const Foo = (props: IFoo) => {
return <button onClick={props.handleClick}></button>
}
You have two options:
interface IFoo {
handleClick(e: MouseEvent<HTMLButtonElement>) => void
}
interface IFoo {
handleClick: (e: MouseEvent<HTMLButtonElement>) => void
}