如何检查输入文件是空的，并且如果使用jquery选择png格式，也会显示警报 [英] How to check input file is empty, and also display an alert if png format is selected using jquery

问题描述

 <$> 
 
 c $ c>< input type =filename =filesid =file1style =color：White/> 
< input type =submitvalue =Create/> 
  

单击提交时应该触发检查。

> http://jsfiddle.net/G7xke/

---

 <形式> 
< input type =filename =filesid =file1style =color：White/> 
< input type =submitvalue =Create/> 
< / form> 
   

和JavaScript：

点击（function（）{
 var fileName = $（＃file1）。val（）; 
 if（fileName.lastIndexOf（ （OK）; 
 else 
 alert（Not PNG）; 
}）
  

I have got an input file upload , need to check which file is uploaded / if no file is selected by the client using jquery.

<input type="file" name="files" id="file1" style="color:White" />
<input type="submit" value="Create" />

The check should trigger when submit is clicked.

解决方案

See the sample I have created:

http://jsfiddle.net/G7xke/

---

<form>
<input type="file" name="files" id="file1" style="color:White" />
<input type="submit" value="Create" />
</form>
<button value="check" id="check" name="check" >check</button>

And JavaScript:

$("#check").click(function(){
    var fileName = $("#file1").val();
    if(fileName.lastIndexOf("png")===fileName.length-3)
        alert("OK");
    else
        alert("Not PNG");
})

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