Javascript 如何在jQuery中检查输入文件是否为空
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How to check if input file is empty in jQuery
提问by user3753569
Brand new to JS.
I am trying to check if the file input element is empty when submitting the form with jQuery/JavaScript.
I have gone through a bunch of solutions and nothing is working for me. I am trying to avoid the /c/fakepath(unless there is no other option)
全新的 JS。
我试图在使用 jQuery/JavaScript 提交表单时检查文件输入元素是否为空。我已经经历了一堆解决方案，但没有什么对我有用。我试图避免/c/fakepath（除非没有其他选择）
<input type="file" name="videoFile" id="videoUploadFile" />
This does not work:
这不起作用：
var vidFile = $("#videoUploadFile").value;
The only way I can get the filename is if I use the following:
我可以获得文件名的唯一方法是使用以下内容：
var vidFile = document.getElementById("videoUploadFile").files[0].name;
If there is no file available the code throws an error:
如果没有可用的文件，代码会抛出错误：
cannot read property name of undefined
无法读取未定义的属性名称
which makes sense because the array is not set. but I cannot figure out how to do any error handling with this.
这是有道理的，因为未设置数组。但我无法弄清楚如何对此进行任何错误处理。
How do I properly grab the file input element videoUploadFile, check if it's empty, throw an error message if it's empty?
如何正确获取文件输入元素videoUploadFile，检查它是否为空，如果为空则抛出错误消息？
回答by Patrick Evans
回答by Salim
Here is the jQuery version of it:
这是它的 jQuery 版本：
if ($('#videoUploadFile').get(0).files.length === 0) {
console.log("No files selected.");
}
回答by Mamun
To check whether the input file is empty or not
by using the file length property, indexshould be specified like the following:
要使用文件长度属性检查输入文件是否为空，index应指定如下：
var vidFileLength = $("#videoUploadFile")[0].files.length;
if(vidFileLength === 0){
alert("No file selected.");
}
回答by Adnan Limdiwala
Questions : how to check File is empty or not?
问题：如何检查文件是否为空？
Ans: I have slove this issue using this Jquery code
Ans：我使用这个 Jquery 代码解决了这个问题
//If your file Is Empty :
if (jQuery('#videoUploadFile').val() == '') {
$('#message').html("Please Attach File");
}else {
alert('not work');
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" id="videoUploadFile">
<br>
<br>
<div id="message"></div>回答by Joel Youngberg
I know I'm late to the party but I thought I'd add what I ended up using for this - which is to simply check if the file upload input does not contain a truthy value with the not operator & JQuery like so:
我知道我参加聚会迟到了，但我想我会添加我最终为此使用的内容 - 这是简单地检查文件上传输入是否不包含带有 not 运算符和 JQuery 的真实值，如下所示：
if (!$('#videoUploadFile').val()) {
alert('Please Upload File');
}
Note that if this is in a form, you may also want to wrap it with the following handler to prevent the form from submitting:
请注意，如果这是在表单中，您可能还需要使用以下处理程序包装它以防止表单提交：
$(document).on("click", ":submit", function (e) {
if (!$('#videoUploadFile').val()) {
e.preventDefault();
alert('Please Upload File');
}
}
