如何在 JavaScript 中获取最近的 span 元素

Posted 2023-03-07

【中文标题】如何在 JavaScript 中获取最近的 span 元素

【英文标题】：How to get the closest span element in JavaScript

【发布时间】：2021-02-16 03:51:23

【问题描述】：

在我的刀片模板中，我有这个：

<form method="POST" action=" route('excon.xlsx.upload') " enctype="multipart/form-data">
    <div class="border-dashed border-2 w-64 h-32 rounded flex justify-center items-center" id="file-uploader">
            <svg version="1.1" class="h-8 text-grey mr-2" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" 
                 viewBox="0 0 60 60" style="enable-background:new 0 0 60 60;" xml:space="preserve">
                <g>
                    <path d="M50.975,20.694c-0.527-9-7.946-16.194-16.891-16.194c-5.43,0-10.688,2.663-13.946,7.008
                          c-0.074-0.039-0.153-0.065-0.228-0.102c-0.198-0.096-0.399-0.188-0.605-0.269c-0.115-0.045-0.23-0.086-0.346-0.127
                          c-0.202-0.071-0.406-0.133-0.615-0.19c-0.116-0.031-0.231-0.063-0.349-0.09c-0.224-0.051-0.452-0.09-0.683-0.124
                          c-0.102-0.015-0.202-0.035-0.305-0.047C16.677,10.523,16.341,10.5,16,10.5c-4.962,0-9,4.037-9,9c0,0.129,0.007,0.255,0.016,0.381
                          C2.857,22.148,0,26.899,0,31.654C0,38.737,5.762,44.5,12.845,44.5H18c0.552,0,1-0.447,1-1s-0.448-1-1-1h-5.155
                          C6.865,42.5,2,37.635,2,31.654c0-4.154,2.705-8.466,6.432-10.253L9,21.13V20.5c0-0.123,0.008-0.249,0.015-0.375l0.009-0.175
                          l-0.012-0.188C9.007,19.675,9,19.588,9,19.5c0-3.859,3.14-7,7-7c0.309,0,0.614,0.027,0.917,0.067
                          c0.078,0.01,0.155,0.023,0.232,0.036c0.268,0.044,0.532,0.102,0.792,0.177c0.034,0.01,0.069,0.016,0.102,0.026
                          c0.286,0.087,0.565,0.198,0.838,0.322c0.069,0.031,0.137,0.065,0.205,0.099c0.242,0.119,0.479,0.251,0.707,0.399
                          C21.72,14.875,23,17.039,23,19.5c0,0.553,0.448,1,1,1s1-0.447,1-1c0-2.754-1.246-5.219-3.2-6.871
                          C24.666,8.879,29.388,6.5,34.084,6.5c7.744,0,14.178,6.135,14.848,13.887c-1.022-0.072-2.553-0.109-4.083,0.125
                          c-0.546,0.083-0.921,0.593-0.838,1.139c0.075,0.495,0.501,0.85,0.987,0.85c0.05,0,0.101-0.004,0.152-0.012
                          c2.224-0.336,4.543-0.021,4.684-0.002C54.49,23.372,58,27.661,58,32.472C58,38.001,53.501,42.5,47.972,42.5H44
                          c-0.552,0-1,0.447-1,1s0.448,1,1,1h3.972C54.604,44.5,60,39.104,60,32.472C60,26.983,56.173,22.06,50.975,20.694z"/>
                    <path d="M31.708,30.794c-0.092-0.093-0.203-0.166-0.326-0.217c-0.244-0.101-0.52-0.101-0.764,0
                          c-0.123,0.051-0.233,0.124-0.326,0.217l-7.999,7.999c-0.391,0.391-0.391,1.023,0,1.414C22.488,40.402,22.744,40.5,23,40.5
                          s0.512-0.098,0.707-0.293L30,33.914V54.5c0,0.553,0.448,1,1,1s1-0.447,1-1V33.914l6.293,6.293C38.488,40.402,38.744,40.5,39,40.5
                          s0.512-0.098,0.707-0.293c0.391-0.391,0.391-1.023,0-1.414L31.708,30.794z"/>
                </g>
            </svg>
            <!-- Auto submit -->
            <span class="block text-grey">Drop your image file here</span>
            <input type="file" name="spreadsheet" id="spreadsheet-file" class="sm:hidden" />
        </div>
        <div class='mt-6 sm:hidden'>
            To update the Event's MEL, simply drag and drop your image file above.
        </div>
</form>

我的 javascript 看起来像这样：

window.onload = () => 
    document.getElementById('file-uploader').addEventListener('click', () => 
        document.getElementById('spreadsheet-file').click();
    );
    
    document.getElementById('file-uploader').addEventListener('change', updateFileInfo);
;

function updateFileInfo(event) 
    let val = event.target.value;
    document.getElementById('file-uploader').closest('span').innerhtml = val;

我要更新

<span class="block text-grey">Drop your image file here</span>

但是我得到了这个文件的名称：

Uncaught TypeError: document.getElementById(...).closest(...) is null

【问题讨论】：

最接近的（）方法遍历元素及其父元素（朝向文档根），直到找到与提供的选择器字符串匹配的节点 - 参见@ 987654321@

【参考方案1】：

closest() 方法在 DOM 树中搜索与指定 CSS 选择器匹配的最接近的元素。它从元素本身开始，然后测试父级、祖父级等，直到找到匹配项。如果未找到匹配项，则此方法返回 null。

所以在你的情况下，如果你想访问跨度，你可以修改你的javascript如下：

document.getElementById('file-uploader').querySelector('span').innerHTML = val;

解决方案是基于你的 HTML 结构，目前你只有一个 span 标签，所以它可以工作。

【参考方案2】：

作为库马尔回答的补充；

document.getElementById('file-uploader').querySelector('span').innerHTML = val;

如果您只是更新文本，我建议您使用 innerText。

document.querySelector('#file-uploader > span').innerText = val;