php - jQuery form plugin, how to prevent the form submit -

i using jquery form plugin upload file , show progress bar.

the js code :

var bar = $('.bar'); var percent = $('.percent'); var status = $('#status');  var options = {      target:     '.result',      url:        'slider_insert_now.php',         beforesend: function() {       var img_file = $.trim($(".img_file").val());      if(img_file==$.trim('')){      $(".result").html('<span class="error">no file selected</span>');       return false;       }else{      status.empty();     var percentval = '0%';     bar.width(percentval)     percent.html(percentval);      return true;  }   }, uploadprogress: function(event, position, total, percentcomplete) { var percentval = percentcomplete + '%'; bar.width(percentval) percent.html(percentval); }, success: function() { var percentval = '100%'; bar.width(percentval) percent.html(percentval); }, complete: function(xhr) { status.html(xhr.responsetext); }    };     $('#form_upload').ajaxform(options); 

and html:

<div class="result"></div>       <form id="form_upload" action="javascript:void(0)" method="post" enctype="multipart/form-data">      <div class="progress"> <div class="bar"></div> <div class="percent">0%</div> </div> <div id="status"></div>        <input type="file" value="" name="img_file" class="img_file" />      <br></br>      <input type="submit" value="upload image" />       </form> 

in beforesend function, used return false prevent form submitting itself. not work . how can achieve that?

in html remove javascript:void(0) , put # instead, , use event.preventdefault(); ever trigger submit. this:

$(document).on('click', '#submitname', function (event) {  event.preventdefault();   $.ajax({     url: 'somepage.php',     type: 'post',     datatype:'html',        data: $('#formname').serialize(),     success: function(response, textstatus, jqxhr){       ///do  },    error: function(jqxhr, textstatus, errorthrown){       console.log('error(s):'+textstatus, errorthrown);    }  }); });