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
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
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