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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)開發一個帶有HTML,JavaScript和CSS3的應用程序
在我的文件上添加文件后,我需要觸發啟用或禁用按鈕的驗證
<input type="file"/>
到目前為止我有這個:
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;
}
}
但我似乎無法使其發揮作用
_uploadCaptureInputFile.addEventListener("onchange", verifyControls, false);
它不服從,是否有辦法將此事件分配給我的inputType以觸發此類驗證?
提前致謝
在使用addEventListener
偵聽時,您將偵聽僅僅是"change"
而不是"onchange"
的更改事件。 聽"onchange"
永遠不會觸發,因為從未觸發匹配事件(除非您自己創建自定義事件)。
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