queryselector_修复流节点问题“未知的属性querySelector”

叁歲伎倆 2023-02-22 01:28 23阅读 0赞

queryselector

![JavaScript Flow React][]

[Flow][], the static type checker used in many React projects, feels like a gift and a curse at times; a gift in that it identifies weaknesses in your code, and a curse that sometimes you feel like you're needlessly adjusting your code to satisfy Flow.  I've grown to appreciate Flow but that doesn't mean I end up spending extra hours finding new ways to code.

[Flow][]是许多React项目中使用的静态类型检查器，有时感觉像是礼物和诅咒。 这是一个礼物，它可以识别代码中的弱点，还有一个诅咒，有时您会觉得自己不必要地调整代码来满足Flow的要求。 我已经对Flow产生了赞赏，但这并不意味着我最终要花费额外的时间来寻找新的编码方法。

I recently ran into an issue where I was querying for a node in a React element and then using `querySelector` on that node to find a child; surprisingly Flow took issue:

最近，我遇到了一个问题：我在React元素中查询一个节点，然后在该节点上使用`querySelector`查找一个子节点。 令人惊讶的是Flow出现了问题：

Cannot call node.querySelector because property querySelector of unknown
    type [1] is not a function.
    
    71│ const { maxHeight } = this.state;
    72│ const node = ReactDOM.findDOMNode(this);
    [1] 73│ if (node && node.querySelector) {
    74│ const popupNode = node.querySelector(".preview-popup");
    75│ if (popupNode) {
    76│ popupNode.style.maxHeight = `${maxHeight}px`;
    77│ }
    
    /private/tmp/flow/flowlib_34a4c903/react-dom.js
    [1] 14│ ): null | Element | Text;
    
    Found 1 error

It turns out that `findDOMNode` can return type `Text`, and thus `querySelectorAll` would be `undefined`;  Flow doesn't like `undefined`.  The solution is to use `instanceOf`  with `HTMLElement`:

事实证明`findDOMNode`可以返回`Text`类型，因此`querySelectorAll`将是`undefined` ； Flow不喜欢`undefined` 。 解决方案是将`instanceOf`与`HTMLElement`一起使用：

if (node instanceOf HTMLElement) {
        // ...
    }

The solution makes sense but a part of me silently rages that `&& node.querySelector` doesn't qualify.  In the end, Flow is so helpful that little changes like this don't get me too wound up.

该解决方案很有意义，但我的一部分默默地`&& node.querySelector`不符合条件。 最后，Flow非常有用，以至于像这样的微小变化都不会使我感到困惑。

> 翻译自: [https://davidwalsh.name/react-node-flow][https_davidwalsh.name_react-node-flow]

queryselector

[JavaScript Flow React]: http://imgconvert.csdnimg.cn/aHR0cHM6Ly9kYXZpZHdhbHNoLm5hbWUvZGVtby9mbG93LWxvZ28ucG5n?x-oss-process=image/format,png
[Flow]: https://flow.org/en/
[https_davidwalsh.name_react-node-flow]: https://davidwalsh.name/react-node-flow