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---
title: 'FileReader: load event'
slug: Web/API/FileReader/load_event
tags:
- load 事件
translation_of: Web/API/FileReader/load_event
---
<div>{{APIRef}}</div>
<p>当文件成功读取时，执行<code>load</code> 事件</p>
<table class="properties">
<tbody>
<tr>
<th scope="row">是否冒泡</th>
<td>No</td>
</tr>
<tr>
<th scope="row">是否能中断退出</th>
<td>No</td>
</tr>
<tr>
<th scope="row">调用接口</th>
<td>{{domxref("ProgressEvent")}}</td>
</tr>
<tr>
<th scope="row">事件处理属性</th>
<td>{{domxref("FileReader.onload")}}</td>
</tr>
</tbody>
</table>
<h2 id="例子">例子</h2>
<h3 id="Live_example">Live example</h3>
<h4 id="HTML">HTML</h4>
<pre class="brush: html"><div class="example">
<div class="file-select">
<label for="avatar">Choose a profile picture:</label>
<input type="file"
id="avatar" name="avatar"
accept="image/png, image/jpeg">
</div>
<img src="" class="preview" height="200" alt="Image preview...">
<div class="event-log">
<label>Event log:</label>
<textarea readonly class="event-log-contents"></textarea>
</div>
</div></pre>
<div class="hidden">
<h4 id="CSS">CSS</h4>
<pre class="brush: css">img.preview {
margin: 1rem 0;
}
.event-log-contents {
width: 18rem;
height: 5rem;
border: 1px solid black;
margin: .2rem;
padding: .2rem;
}
.example {
display: grid;
grid-template-areas:
"select log"
"preview log";
}
.file-select {
grid-area: select;
}
.preview {
grid-area: preview;
}
.event-log {
grid-area: log;
}
.event-log>label {
display: block;
}
.event-log-contents {
resize: none;
}</pre>
</div>
<h4 id="JS">JS</h4>
<pre class="brush: js">const fileInput = document.querySelector('input[type="file"]');
const preview = document.querySelector('img.preview');
const eventLog = document.querySelector('.event-log-contents');
const reader = new FileReader();
function handleEvent(event) {
eventLog.textContent = eventLog.textContent + `${event.type}: ${event.loaded} bytes transferred\n`;
if (event.type === "load") {
preview.src = reader.result;
}
}
function addListeners(reader) {
reader.addEventListener('loadstart', handleEvent);
reader.addEventListener('load', handleEvent);
reader.addEventListener('loadend', handleEvent);
reader.addEventListener('progress', handleEvent);
reader.addEventListener('error', handleEvent);
reader.addEventListener('abort', handleEvent);
}
function handleSelected(e) {
eventLog.textContent = '';
const selectedFile = fileInput.files[0];
if (selectedFile) {
addListeners(reader);
reader.readAsDataURL(selectedFile);
}
}
fileInput.addEventListener('change', handleSelected);
</pre>
<h4 id="结果">结果</h4>
<p>{{ EmbedLiveSample('Live_example', '100%', '300px') }}</p>
<h2 id="规范">规范</h2>
<table class="standard-table">
<thead>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
</tr>
</thead>
<tbody>
<tr>
<td>{{SpecName('File API', '#dfn-load-event')}}</td>
<td>{{Spec2('File API')}}</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{Compat("api.FileReader.load_event")}}</p>
<h2 id="请参阅">请参阅</h2>
<ul>
<li>Related events: {{domxref("FileReader.loadstart_event")}}, {{domxref("FileReader.loadend_event")}}, {{domxref("FileReader.progress_event")}}, {{domxref("FileReader.error_event")}}, {{domxref("FileReader.abort_event")}}</li>
</ul>
|
