on change event for file input element

问题

I have 4 file inputs that I want them trigger upload proccess when their value is changed. I mean when you select a picture and click open on select image dialog, the script to upload the picture be triggered. I've used onchange event but I think this is not the right event:

JS:

$("input[type=file]").on('change',function(){
    alert(this.val());//I mean name of the file
});

HTML:

<div class="form-group col-md-11 col-md-offset-1">
    <input type="file" name="photos[]">
    <input type="file" name="photos[]">
    <input type="file" name="photos[]">
    <input type="file" name="photos[]">
</div>

What should I do?

回答1:

The OnChange event is a good choice. But if a user select the same image, the event will not be triggered because the current value is the same as the previous.

The image is the same with a width changed, for example, and it should be uploaded to the server.

To prevent this problem you could to use the following code:

$(document).ready(function(){
    $("input[type=file]").click(function(){
        $(this).val("");
    });

    $("input[type=file]").change(function(){
        alert($(this).val());
    });
});

回答2:

Use the files filelist of the element instead of val()

$("input[type=file]").on('change',function(){
    alert(this.files[0].name);
});

回答3:

Give unique class and different id for file input

           $("#tab-content").on('change',class,function()
               {
                  var id=$(this).attr('id');
                      $("#"+id).trigger(your function); 
               //for name of file input  $("#"+id).attr("name");
               });

回答4:

For someone who want to use onchange event directly on file input, set onchange="somefunction(), example code from the link:

<html>
<body>
    <script language="JavaScript">
    function inform(){
        document.form1.msg.value = "Filename has been changed";
    }
    </script>
    <form name="form1">
    Please choose a file.
    <input type="file" name="uploadbox" size="35" onChange='inform()'>
    <br><br>
    Message:
    <input type="text" name="msg" size="40">
    </form>
</body>
</html>

来源：https://stackoverflow.com/questions/20244327/on-change-event-for-file-input-element

标签

javascript

jquery

html

upload