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[英]How do I check if a file has been selected in a <input type=“file”> element?
[英]How to check an input type=“file” has a file selected?
我正在使用VS2012(MetroApp)开发一个带有HTML,JavaScript和CSS3的应用程序
在我的文件上添加文件后,我需要触发启用或禁用按钮的验证
<input type="file"/>
到目前为止我有这个:
HTML:default.html:
<!DOCTYPE html>
<html>
<head>
<title>myApp</title>
<link href="/css/default.css" rel="stylesheet" />
<script src="/js/default.js"></script>
</head>
<body>
<div id="content">
<h1>myApp</h1>
<br /><br />
<button id="imageCaptureButton">Take Picture</button>
<input type="file" id="uploadCaptureInputFile"/><br />
<button id="uploadCaptureButton">Subir Foto</button>
<br /><br />
<div id="result"></div>
</div>
</body>
</html>
JavaScript:default.js
function getDomElements() {
_uploadCaptureButton = document.querySelector("#uploadCaptureButton");
_uploadCaptureInputFile = document.querySelector("#uploadCaptureInputFile");
}
function wireEventHandlers() {
_uploadCaptureInputFile.addEventListener("onchange", verifyControls, false);
}
app.onloaded = function () {
getDomElements();
wireEventHandlers();
_uploadCaptureButton.disabled = true;
}
function verifyControls() {
if ( _uploadCaptureInputFile != "") {
_uploadCaptureButton.disabled = false;
}
else {
_uploadCaptureButton.disabled = true;
}
}
但我似乎无法使其发挥作用
_uploadCaptureInputFile.addEventListener("onchange", verifyControls, false);
它不服从,是否有办法将此事件分配给我的inputType以触发此类验证?
提前致谢
在使用addEventListener
侦听时,您将侦听仅仅是"change"
而不是"onchange"
的更改事件。 听"onchange"
永远不会触发,因为从未触发匹配事件(除非您自己创建自定义事件)。
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