删除验证并自动选择默认缩略图图像

Question

I am using a PHP script which has a module of Article Posting User needs to select a thumbnail else it gives an error. I want to remove mandatory validation, and when user has not selected any Thumnail, then it should select a default image somewhere from directory.

PHP Page:

    <div id="thumbselect" class="hide bd margin-bottom-20 box">
    <div class="upload-header">
     <span><?= Lang::get('post_thumb_head') ?></span>
     <a title="<?= Lang::get('upload_thumb') ?>" class="sendimg upload-image tip" href="#"><i class="pe-none icon-upload2"></i></a>
  </div>
  <div class="rightbox">
     <div class="preview cover"><img src="Template/Images/imgplaceholder.jpg" class="topimg sendimg" style="opacity: 1;"></div>
    </div>
   </div>
    <div id="photocover" class="hide">
     <div class="upload-header">
     <span><?= Lang::get('post_thumb_head') ?></span>
    </div>
    <div id="thmb" class="rightbox bd">
     <div id="thmbinner" class="preview"></div>
     <a href="#" class="tmb left"><i class="icon-angle-left"></i></a>
     <a href="#" class="tmb right"><i class="icon-angle-right"></i></a>
  </div>
  </div>
  <div id="frameselect" class="hide">
  <a id="setframe" class="bttn bttn-primary selectframe" style="display:block;margin:4px;"><?= Lang::get('select_another_frame') ?></a>
  <div id="mp4preview" class="rightbox bd hide"></div>
  </div>

JavaScript page

     define(["jquery","utils","tinyMCE"],function(e,t){var n,a={File:t.Query("#file"),Tags:t.Query("#input-tags"),Form:t.Query("#submitArticle"),Thumb:t.Query("#thumbselect"),AddImg:t.Query(".sendimg")},r={Init:function(){t.ResetCache(),r.initMCE(),r.setEvents(),r.setPlugins()},initMCE:function(){require(["tinycfg","tinyMCE"],function(e){tinyMCE.init(t.Extend(e.extended,{file_browser_callback:function(e,t,r,i){"image"==r&&(n="art",a.File.click())}}))})},UploadFile:function r(){var i=new FormData,o=new t.NodeCache,s=new XMLHttpRequest,u=a.File.files[0],g=o.FindElems({line:"#progress-bar",total:"#progress-total",status:"#progress-status",progress:".progress"});r.progress=function(e){g.total.innerHTML=Lang.get("prefix_uploaded")+" "+(e.loaded/1048576).toFixed(2)+" "+Lang.get("of")+" "+(e.total/1048576).toFixed(2)+" MB";var t=e.loaded/e.total*100;g.line.value=Math.round(t),g.status.innerHTML=Math.round(t)+"%"},r.complete=function(a){var r=a.target.responseText,i=JSON.parse(r);"thumb"!=n?(e(g.progress).delay(2500).slideUp(1e3),"duplicate"==i.status?t.Info("error",Lang.get("note_error_head"),Lang.get("img_exists")):tinyMCE.activeEditor.execCommand("mceInsertContent",!1,'<img style="width: 100%" src=\'Uploads/Temp/'+i.userdir+"/"+i.filename+"'>"),g.status.innerHTML=Lang.get("img_uploaded")):t.Query(".topimg").src="Uploads/Temp/"+i.userdir+"/"+i.filename},r.error=function(e){g.status.innerHTML=Lang.get("an_error_occured")},"image/jpeg"==u.type||"image/png"==u.type?(g.line.value=0,"art"==n&&e(g.progress).slideDown(1e3),t.Info("info",Lang.get("please_wait"),Lang.get("uploading_img")),t.Query(".mce-close")&&t.Query(".mce-close").click(),i.append("file",u),i.append("option","thumbnail"),"thumb"==n&&i.append("hash","cover"),s.upload.onprogress=r.progress,s.addEventListener("load",r.complete,!1),s.addEventListener("error",r.error,!1),s.open("POST",t.Path.Image),s.send(i)):(t.Query(".mce-close").click(),t.Info("error",Lang.get("img_invalid_head"),Lang.get("img_invalid_ext")))},setPlugins:function(){e(a.Tags).tagsInput(),e(a.Thumb).fadeIn()},setEvents:function(){PubSub.subscribe("unload",t.ResetCache),a.File.addEventListener("change",r.UploadFile),a.Form.addEventListener("submit",r.Submit),a.AddImg.forEach(function(e){e.addEventListener("click",r.SendImage)})},SendImage:function(e){e.preventDefault(),n="thumb",t.Query("#file").click()},Submit:function(n){n.preventDefault();var i=t.ParseForm.call(this);return i.Data.type="article",i.Data.desc=tinyMCE.get("art_content").getContent(),e.ajax({type:"POST",url:t.Path.Subm,data:i.Data,beforeSend:function(){t.Loading(Lang.get("please_wait"))},success:function(n){t.Loading(Lang.get("please_wait")),1!=n?t.Info("error",Lang.get("an_error_occured"),n):(t.Query(".topimg").src="Template/Images/imgplaceholder.jpg",e(a.Thumb).hide(),t.Info("success",Lang.get("success"),Lang.get("post_submitted")),r.ResetForm()),t.Loading("close")}}),!1},ResetForm:function(){a.Form.reset(),tinyMCE.get("art_content").setContent("");for(var e=document.getElementsByClassName("tag");e[0];)e[0].parentNode.removeChild(e[0])}};r.Init()});

Thumbnail goes to /Uploads/Media/Mar19/Sat30/291/cover.jpg.