如何在Reactjs中创建动态字段

总之，这可以通过在select元素上触发onchange事件来实现。目前尚不清楚您要做什么，但我相信这与这种情况类似

class Form extends Component {
  constructor() {
    super()
    this.state = {
      options: []
    }
  }

  addOperation(e) {
    const selectedValue = this.refs.selection.value
    const currentOptions = this.state.options
    currentOptions.push(selectedValue);

    // append selected value to the state's options array on every change
    this.setState({ options: currentOptions })
  }

  renderRows() {
    // this is where you'll define each type of row
    this.state.options.map((option, index) => {
      if (option === "add") {
        return (
          <tr class="form-row" key={index}>
            <td>Adjust Price (Add)</td>
            <td>
              <label>
                Add
                <input type="text" placeholder={option} />
              </label>
                to
              <select>
                <option value="option1">option1</option>
                <option value="option2">option2</option>
                <option value="option3">option3</option>
              </select>
            </td>
            <td>
              <button>Remove</button>
            </td>
          </tr>
        )
      } else if (option === "multiply") {
        return (
          <tr class="form-row" key={index}>
            <td>Adjust Price (Multiply)</td>
            <td>
              <label>
                Multiply
                <input type="text" placeholder={option} />
              </label>
                to
              <select>
                <option value="option1">option1</option>
                <option value="option2">option2</option>
                <option value="option3">option3</option>
              </select>
            </td>
            <td>
              <button>Remove</button>
            </td>
          </tr>
        )
      } else if (option === "equals") {
        // return a different row here
      } else if (option === "not equals") {
        // return a different row here
      }
    })
  }

  render () {
    return (
      <form>
        <div className="appended-inputs">
          {renderRows.bind(this)}
        </div>
        <select name="select" id="select" ref="selection">
          <option value="add">Adjust Price (Add)</option>
          <option value="multiply">Adjust Price (Multiply)</option>
          <option value="equals">Filter Products (equals)</option>
          <option value="not equals">Filter Products (not equals)</option>
        </select>
        <button onClick={addOperation.bind(this)}>Add Operation</button>
      </form>
    )
  }
}

本质上，这里发生的是我们在组件状态上存储了一组选项，最初是空的。现在，当用户选择某项并添加一个操作时，它将添加到状态数组中。在renderRows函数中，您具有一系列if / if else来决定要返回哪种行，或者可以使用switch块。

因此，现在当用户在下拉菜单中选择某项并单击添加操作时，将立即附加一个新的输入字段。