Typescript input onchange event.target.value
In my react and typescript app, I use: onChange={(e) => data.motto = (e.target as any).value}
.
How do I correctly define the typings for the class, so I wouldn't have to hack my way around the type system with any
?
export interface InputProps extends React.HTMLProps<Input> {
...
}
export class Input extends React.Component<InputProps, {}> {
}
If I put target: { value: string };
I get :
ERROR in [default] /react-onsenui.d.ts:87:18
Interface 'InputProps' incorrectly extends interface 'HTMLProps<Input>'.
Types of property 'target' are incompatible.
Type '{ value: string; }' is not assignable to type 'string'.
Generally event handlers should use e.currentTarget.value
, e.g.:
onChange = (e: React.FormEvent<HTMLInputElement>) => {
const newValue = e.currentTarget.value;
}
You can read why it so here (Revert "Make SyntheticEvent.target generic, not SyntheticEvent.currentTarget.").
UPD: As mentioned by @roger-gusmao ChangeEvent
more suitable for typing form events.
onChange = (e: React.ChangeEvent<HTMLInputElement>)=> {
const newValue = e.target.value;
}
the correct way to use in TypeScript is
handleChange(e: React.ChangeEvent<HTMLInputElement>) {
// No longer need to cast to any - hooray for react!
this.setState({temperature: e.target.value});
}
render() {
...
<input value={temperature} onChange={this.handleChange} />
...
);
}
Follow the complete class, it's better to understand:
import * as React from "react";
const scaleNames = {
c: 'Celsius',
f: 'Fahrenheit'
};
interface TemperatureState {
temperature: string;
}
interface TemperatureProps {
scale: string;
}
class TemperatureInput extends React.Component<TemperatureProps, TemperatureState> {
constructor(props: TemperatureProps) {
super(props);
this.handleChange = this.handleChange.bind(this);
this.state = {temperature: ''};
}
// handleChange(e: { target: { value: string; }; }) {
// this.setState({temperature: e.target.value});
// }
handleChange(e: React.ChangeEvent<HTMLInputElement>) {
// No longer need to cast to any - hooray for react!
this.setState({temperature: e.target.value});
}
render() {
const temperature = this.state.temperature;
const scale = this.props.scale;
return (
<fieldset>
<legend>Enter temperature in {scaleNames[scale]}:</legend>
<input value={temperature} onChange={this.handleChange} />
</fieldset>
);
}
}
export default TemperatureInput;