FileReader: load event
当文件成功读取时,执行load
事件
是否冒泡 | No |
---|---|
是否能中断退出 | No |
调用接口 | ProgressEvent |
事件处理属性 | FileReader.onload |
例子
Live example
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>
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);
结果
规范
Specification |
---|
File API # dfn-load-event |
File API # dfn-onload |
浏览器兼容性
BCD tables only load in the browser