reactjs / reactjs/react.dev

Conditionally controlled component with `value` and `defaultValue` properties

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JavaScript
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描述

In our project codebase there is an uncontrolled component that allows you to specify an initial value with value property (code examples are simplified just to show an idea):


const CustomInput = ({ value = '', onChange }) => {
  const [uncontrolledValue, setUncontrolledValue] = useState(value);

  const handleChange = (e) => {
    setUncontrolledValue(e.target.value);
    if (onChange) {
      onChange(e.target.value);
    }
  }

  return <input value={uncontrolledValue} onChange={handleChange} />
}

This component is used inside the complex form (other input components in this form are controlled). Resetting the form causes problems with this particular component because it doesn't update the internal value on props change. There is the article that recommends 2 possible solutions:

  • rewrite component to be controlled one
  • trigger force rerender of the component using key property

IMO there is another option available - make component controlled/uncontrolled depending on existence value property:


const CustomInput = ({ value: controlledValue, defaultValue = '', onChange }) => {
  const [uncontrolledValue, setUncontrolledValue] = useState(defaultValue);
  const isControlled = value !== undefined;
  const value = isControlled ? controlledValue : uncontrolledValue;

  const handleChange = (e) => {
    if (!isControlled) {
      setUncontrolledValue(e.target.value);
    }

    if (onChange) {
      onChange(e.target.value);
    }
  }

  return <input value={value} onChange={handleChange} />
}

This approach allows custom components to act as a standard <input /> element. I saw it in @kentcdodds video lesson and also in some popular libraries sources. But I can't find anything about such an approach in official react documentation. defaultValue is mentioned only here:

Should this approach be added as a recommendation in You Probably Don't Need Derived State or Forms article? If not are there any pitfalls to consider it as bad practice / anti-pattern?

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研究方向

從 issue 中連結的「You Probably Don’t Need Derived State」、Forms 和 Uncontrolled Components 文件開始。將其中現有的指引與此處描述的 controlled/uncontrolled component pattern 進行比較,然後判斷是否有必要修改文件,以及修改內容應該放在哪裡。

由索引模型根據 Issue 內容生成。

評估

技術堆疊
javascript, react
領域
documentation
Issue 類型
文件
難度
5/5
預估耗時
一週以上
活躍度
停滯
描述清晰度
需要釐清
新手友好度
25/100

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