单击文件上传按钮后延迟？

Question

当我点击“选择要上传的文件”（即输入类型=文件）时，我点击按钮并选择文件到在按钮旁边显示所选文件之间存在延迟。浏览器是否尝试将文件加载到浏览器中？为什么会有延迟。

后续，如何在选择文件后立即显示“请稍候..”消息。我尝试了各种 JQ 选项，似乎所有选项都在初始延迟后触发（正如我所说的，可能是浏览器正在尝试加载不确定的文件）我想用加载器小部件/消息来覆盖延迟。

请帮忙。

Answer 1

方法是使用buttonto 元素来触发同级 toclick对话框；将“正在加载”小部件附加到文档；当用户重新选择文件或关闭对话框时，利用附加事件来删除“正在加载”小部件。input type="file"Open File.one()focus$(window)windowfocusOpen File

$("button").click(function() {
  var spinner = $("<img />", {
    "id": "spinner",
    "src": "data:image/gif;charset=binary;base64,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"
});
  $(this).after(spinner).nextAll("input:first").click();
  $(window).one("focus", function() {
    $("#spinner").detach()
  })
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js">
</script>
<button>choose file</button>
<input type="file" style="opacity:0;"/>