如何检查输入类型=“文件”是否选择了文件？

Question

I am developing an app with HTML, JavaScript and CSS3 with VS2012 (MetroApp) 我正在使用VS2012（MetroApp）开发一个带有HTML，JavaScript和CSS3的应用程序

I need to trigger a verification for enabling or disabling a button after adding a file on my 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"/>

so far I have this: 到目前为止我有这个：

HTML: default.html: 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 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;
    }
}

But I can't make it work, it seems that 但我似乎无法使其发挥作用

_uploadCaptureInputFile.addEventListener("onchange", verifyControls, false);

it doesn't obey, is there a way to assign this event to my inputType for trigger such verification?? 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？

thanks in advance 提前致谢

Answer 1

When listening with addEventListener , you listen for the change event which is just "change" , not "onchange" . 在使用addEventListener侦听时，您将侦听仅仅是"change"而不是"onchange"的更改事件。 Listening for "onchange" will never fire because there is never a matching event fired (unless you create a custom one yourself). 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）。

如何检查输入类型=“文件”是否选择了文件？

问题描述

1 个解决方案

解决方案1
2 已采纳 2013-11-29 20:03:30

如何检查输入类型=“文件”是否选择了文件？

问题描述

1 个解决方案

解决方案1 2 已采纳 2013-11-29 20:03:30

解决方案1
2 已采纳 2013-11-29 20:03:30