将字符串转换为数字简单答案

<input
    type="text"
    value={incrementAmount}
    onChange={(e) => {
      setIncrementAmmount(+e.target.value);
    }}
/>

一般情况下，事件处理程序应该使用e. currentarget。值,例如:

const onChange = (e: React.FormEvent<HTMLInputElement>) => {
  const newValue = e.currentTarget.value;
}

你可以在这里读到为什么会这样(还原“Make SyntheticEvent。target generic，而不是syntheticevent . currentarget .")。

UPD:正如@roger-gusmao提到的，ChangeEvent更适合输入表单事件。

const onChange = (e: React.ChangeEvent<HTMLInputElement>) => {
  const newValue = e.target.value;
}

as HTMLInputElement为我工作

在TypeScript中使用的正确方法是

  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} />
        ...
    );
  }

遵循完整的类，更好地理解:

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;

const handleChange = (
    e: ChangeEvent<HTMLInputElement>
  ) => {
    const { name, value } = e.target;
    this.setState({ ...currentState, [name]: value });
  };

您可以将此应用于表单组件中的每个输入元素

const event = { target: { value: 'testing' } as HTMLInputElement };
handleChangeFunc(event as ChangeEvent<HTMLInputElement>);

这对我很有用。