JS:How to send multiple files using FormData(jQuery Ajax)

You have an error in javascript: you're iterating only over files in one input please have a look at this

var ajaxData = new FormData();
ajaxData.append( 'action','uploadImages');
$.each($("input[type=file]"), function(i, obj) {
        $.each(obj.files,function(j, file){
            ajaxData.append('photo['+j+']', file);
        })
});

example on jsfiddle

in front end

<form name="uploadImages" method="post" enctype="multipart/form-data">
    <input type="file" name="photo[]" value=""/>
    <input type="file" name="photo[]" value=""/>
    <input type="file" name="photo[]" value=""/>
    <button id="btn">btn</button>
</form>
        <script>
            $(function(){
     var ajaxData = new FormData();
     ajaxData.append( 'action','uploadImages');
     $.each($("input[type=file]"), function(i, obj) {
        $.each(obj.files,function(j, file){
            ajaxData.append('photo['+j+']', file);
          $('#btn').on('click',function(){
        $.ajax({
        url:'https://stores-govan.c9users.io/test',
          type:"POST",
          data:ajaxData,
          processData:false,
          contentType:false,
          success:function(){
            },
          crossDomain:true
        })
        })

        })
     });

})
</script>

at the backend (nodejs) add this(using multer)

var multer=require('multer')
app.post('/test',upload.array('photo[]',6),function(req ,res,next){
            var images=[]
               if(req.files){
               for(var i=0;i<req.files.length;i++){
               images[i]=req.files[i].filename }
               }
               console.log(images)
        })