Условное обновление значения React Json

вам просто нужно событие onChange для обновления состояния на основе имени входных значений

handleChangeEvent = (e) => {
   this.setState({ [e.target.name]: e.target.value })
}

//On your inputs
<input 
    className = "amount" 
    name = "amount" 
    type = "text" 
    placeholder = "Enter Amount"
    value = {this.state.amount}
    onChange = {() => this.handleChangeEvent(e)}
/>

class Updater extends React.Component {
  constructor() {
    super();
    this.state = {
      amount: 0,
      description: "",
      _from: true,
      _to: false,
      date: new Date()
    };
  }

  onAmountChange = e => {
    this.setState({
      amount: e.target.value
    });
  };
  onDescriptionChange = e => {
    this.setState({
      description: e.target.value
    });
  };
  onSelectTypeChange = e => {
    console.info(e.target.value);
    this.setState({
      [e.target.value === "from" ? "_from" : "_to"]: true,
      [e.target.value !== "from" ? "_from" : "_to"]: false
    });
    if (e.target.value !== "from" && (this.state.from != null || this.state.from !== "")) { 
      this.setState({
        to: this.state.from,
        from: null
      });
    } else if (e.target.value === "from" && (this.state.to != null || this.state.to !== "")){
      this.setState({
        from: this.state.to,
        to: null
      });
    }
  };
  onFromToChange = (e) => {
    this.setState({
       [this.state._from ? "from" : "to"]: e.target.value
    });
  }
  onSubmitEdit = () => {
    Axios.put(
      "https://httpbin.org/put",
      {
        ...this.state,  
      },
      { headers: { "Content-Type": "application/json" } }
    )
      .then(response => {
        // handle Response
      })
      .catch(err => {
        // handle Error
      });
  };

  render() {
    return (
      <div className = "updatercontainer">
        <div className = "updaterinputs">
          <input
            onChange = {this.onAmountChange}
            className = "amount"
            name = "amount"
            type = "text"
            placeholder = "Enter Amount"
          />
          <input
            onChange = {this.onDescriptionChange}
            className = "description"
            name = "description"
            type = "text"
            placeholder = "Enter Description"
          />
        </div>
        <div className = "selectbox">
          <select onChange = {this.onSelectTypeChange}>
            <option value = "from">From</option>
            <option value = "to">To</option>
          </select>
          <input onChange = {this.onFromToChange} className = "fromto" type = "text"
               name = "fromto" placeholder = "Enter From or To Name"/>
        </div>
        <div className = "selectboxcontainer">
          <div onClick = {this.onSubmitEdit} className = "button-container">
            <a href = "#" className = "button amount-submit">
              <span>Update</span>
            </a>
          </div>
        </div>
      </div>
    );
  }
}

Подумайте о том, чтобы узнать больше о Обработка входных данных, форм, событий

Рабочая песочница!