使用javascript在文件字段中未选择要上传的文件时弹出警报

Question

hi i am using php and mysql.

i have a form to add record for user. user should prompt when he will not select any file to upload that you want to save data without image.

Can we do that using javascript..

if any one know it would be appreciated..

Thanks in advance

Answer 1

You can verify the file input using javascript.

Here is an example:

function checkFile(yourForm){

    var fileVal = yourForm.elements['fileField'].value;

    //RegEx for valid file name and extensions.
    var pathExpression = "[?:[a-zA-Z0-9-_\.]+(?:.png|.jpeg|.gif)";


    if(fileVal != ""){
        if(!fileVal.toString().match(pathExpression) && confirm("The file is not a valid image. Do you want to continue?")){
            yourForm.submit();
        } else {
            return;
        }
    } else {
        if(confirm("Do you want to continue without adding image?")) {
            yourForm.submit();
        } else {
            return;
        }
    }
}

In your html

<form name="yourForm" method="post" enctype="multipart/form-data"">
    <input type="file" name="fileField" />
    <input type="button" value="submit" onClick="checkFile(this.form)" />
</form>

Note pathExperssion can be customized. Another thing is checking the extension is not too reliable as anyone can inject a file name as extension. Click here for other info.

Answer 2

just check to see if the field is empty and then ask them if that's really what they want...

if( document.forms["uploadForm"].elements["imageField"].value == "" 
     && confirm("You have not added an image, are you sure you want to continue?")
 )
        upload();
    else
        doNothing();