---
title: File.lastModified
slug: Web/API/File/lastModified
tags:
  - API
  - File API
  - Files
translation_of: Web/API/File/lastModified
---
<p>{{APIRef("File API")}}</p>

<p>只读属性 <code><strong>File.lastModified</strong></code> 返回所引用文件最后修改日期， 为自 1970年1月1日0:00 以来的毫秒数。没有已知的最后修改时间则会返回当前时间。</p>

<h2 id="语法">语法</h2>

<pre class="brush:js">var time = <em>instanceOfFile</em>.lastModified;
</pre>

<h2 id="值">值</h2>

<p>自 1970年1月1日0:00 以来的毫秒数。</p>

<h2 id="实例">实例</h2>

<h3 id="从INPUT标签读取文件">从INPUT标签读取文件</h3>

<pre class="brush: html">&lt;input type="file" multiple id="fileInput"&gt;
</pre>

<pre class="brush:js">const fileInput = document.getElementById('fileInput');
fileInput.addEventListener('change', function(event) {
  // files is a FileList object (simliar to NodeList)
  const files = event.target.files;

  for (let i = 0; i &lt; files.length; i++) {
    const date = new Date(files[i].lastModified);
    alert(files[i].name + ' has a last modified date of ' + date);
  }
});
</pre>

<p>结果：</p>

<p>{{ EmbedLiveSample('Reading_from_file_input', 300, 50) }}</p>

<h3 id="动态创建文件">动态创建文件</h3>

<p>如果文件是动态创建的，可以在构造函数{{domxref("File.File()", "new File()")}} 中提供最后修改时间。如果未提供则会继承文件对象被创建时的{{jsxref("Date.now()")}} 。</p>

<pre class="brush:js">var fileWithDate = new File([], 'file.bin', {
  lastModified: new Date(2017, 1, 1),
});
console.log(fileWithDate.lastModified); //returns 1485903600000

var fileWithoutDate = new File([], 'file.bin');
console.log(fileWithoutDate.lastModified); //returns current time
</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('File API', '#file-attrs', 'lastModified')}}</td>
   <td>{{Spec2('File API')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Edge</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>File.lastModified</td>
   <td>13.0</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop("15.0")}}</td>
   <td>10.0</td>
   <td>16.0</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Edge</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Phone</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>File.lastModified</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="参见">参见</h2>

<ul>
 <li>{{domxref("File")}}</li>
</ul>