Typescript input onchange event.target.value - reactjs

Question

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'.

Answer 1

Generally event handlers should use e.currentTarget.value, e.g.:
const 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.
const onChange = (e: React.ChangeEvent<HTMLInputElement>) => {
const newValue = e.target.value;
}

Answer 2

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;

Answer 3

You can do the following:
import { ChangeEvent } from 'react';
const onChange = (e: ChangeEvent<HTMLInputElement>)=> {
const newValue = e.target.value;
}

Answer 4

ChangeEvent<HTMLInputElement> is the type for change event in typescript. This is how it is done-
import { ChangeEvent } from 'react';
const handleInputChange = (event: ChangeEvent<HTMLInputElement>) => {
setValue(event.target.value);
};

Answer 5

we can also use the onChange event fire-up with defined types(in functional component) like as follows:
const handleChange = (
e: React.ChangeEvent<HTMLTextAreaElement | HTMLInputElement>
) => {
const name = e.target.name;
const value = e.target.value;
};

Answer 6

as HTMLInputElement works for me

Answer 7

The target you tried to add in InputProps is not the same target you wanted which is in React.FormEvent
So, the solution I could come up with was, extending the event related types to add your target type, as:
interface MyEventTarget extends EventTarget {
value: string
}
interface MyFormEvent<T> extends React.FormEvent<T> {
target: MyEventTarget
}
interface InputProps extends React.HTMLProps<Input> {
onChange?: React.EventHandler<MyFormEvent<Input>>;
}
Once you have those classes, you can use your input component as
<Input onChange={e => alert(e.target.value)} />
without compile errors. In fact, you can also use the first two interfaces above for your other components.

Answer 8

I use something like this:
import { ChangeEvent, useState } from 'react';
export const InputChange = () => {
const [state, setState] = useState({ value: '' });
const handleChange = (event: ChangeEvent<{ value: string }>) => {
setState({ value: event?.currentTarget?.value });
}
return (
<div>
<input onChange={handleChange} />
<p>{state?.value}</p>
</div>
);
}

Answer 9

When using Child Component We check type like this.
Parent Component:
export default () => {
const onChangeHandler = ((e: React.ChangeEvent<HTMLInputElement>): void => {
console.log(e.currentTarget.value)
}
return (
<div>
<Input onChange={onChangeHandler} />
</div>
);
}
Child Component:
type Props = {
onChange: (e: React.ChangeEvent<HTMLInputElement>) => void
}
export Input:React.FC<Props> ({onChange}) => (
<input type="tex" onChange={onChange} />
)

Answer 10

An alternative that has not been mentioned yet is to type the onChange function instead of the props that it receives. Using React.ChangeEventHandler:
const stateChange: React.ChangeEventHandler<HTMLInputElement> = (event) => {
console.log(event.target.value);
};

Answer 11

Here is a way with ES6 object destructuring, tested with TS 3.3.
This example is for a text input.
name: string = '';
private updateName({ target }: { target: HTMLInputElement }) {
this.name = target.value;
}

Answer 12

This works for me also it is framework agnostic.
const handler = (evt: Event) => {
console.log((evt.target as HTMLInputElement).value))
}

Answer 13

This is when you're working with a FileList Object:
onChange={(event: React.ChangeEvent<HTMLInputElement>): void => {
const fileListObj: FileList | null = event.target.files;
if (Object.keys(fileListObj as Object).length > 3) {
alert('Only three images pleaseeeee :)');
} else {
// Do something
}
return;
}}

Answer 14

Thanks #haind
Yes HTMLInputElement worked for input field
//Example
var elem = e.currentTarget as HTMLInputElement;
elem.setAttribute('my-attribute','my value');
elem.value='5';
This HTMLInputElement is interface is inherit from HTMLElement which is inherited from EventTarget at root level. Therefore we can assert using as operator to use specific interfaces according to the context like in this case we are using HTMLInputElement for input field other interfaces can be HTMLButtonElement, HTMLImageElement etc.
For more reference you can check other available interface here
Web API interfaces by Mozilla
Interfaces in External Node Modules by Microsoft

Answer 15

You no need to type if you do this:
<input onChange={(event) => { setValue(e.target.value) }} />
Because if you set a new value with the arrow function directly in the html tag, typescript will understand by default the type of event.

Answer 16

const handleChange = (
e: ChangeEvent<HTMLInputElement>
) => {
const { name, value } = e.target;
this.setState({ ...currentState, [name]: value });
};
you can apply this on every input element in the form component

Answer 17

function handle_change(
evt: React.ChangeEvent<HTMLInputElement>
): string {
evt.persist(); // This is needed so you can actually get the currentTarget
const inputValue = evt.currentTarget.value;
return inputValue
}
And make sure you have "lib": ["dom"] in your tsconfig.

Answer 18

Convert string to number simple answer
<input
type="text"
value={incrementAmount}
onChange={(e) => {
setIncrementAmmount(+e.target.value);
}}
/>

Answer 19

import { NativeSyntheticEvent, TextInputChangeEventData,} from 'react-native';
// Todo in java script
const onChangeTextPassword = (text : any) => {
setPassword(text);
}
// Todo in type script use this
const onChangeTextEmail = ({ nativeEvent: { text },}: NativeSyntheticEvent<TextInputChangeEventData>) => {
console.log("________ onChangeTextEmail _________ "+ text);
setEmailId(text);
};
<TextInput
style={{ width: '100%', borderBottomWidth: 1, borderBottomColor: 'grey', height: 40, }}
autoCapitalize="none"
returnKeyType="next"
maxLength={50}
secureTextEntry={false}
onChange={onChangeTextEmail}
value={emailId}
defaultValue={emailId}
/>

Answer 20

const event = { target: { value: 'testing' } as HTMLInputElement };
handleChangeFunc(event as ChangeEvent<HTMLInputElement>);
this work for me.