Layui file type and size before upload callback

1. About Layui.upload before before uploading to the file type and file size judgment, block the default upload implementation method "Code is the image upload is wide and high limit processing":

Layui.use ([' Upload ', ' form '),function () {            varUpload =Layui.upload; varform =Layui.form; Upload.render ({elem:' #uploadCover ', URL:'/file/upload.shtml ', Method:"POST", Auto:false//auto parameter must be set to False, Size:"2048", Accept:"File", exts:' Jpg|png|jpeg ', choose:function(obj) { //Pre-Upload Select callback method varFlag =true; Obj.preview (function(index, file, result) {console.log (file); File represents the document information, and result indicates the file src addressvarIMG =NewImage (); IMG.SRC=result; Img.onload=function() {///Initial folder after completion of the upload image to obtain the width of high, to determine the limit of the size of the uploaded image. if(Img.width ==343 && img.height ==240{obj.upload (index, file);//Meet Conditional Call upload method}Else{flag=false; D.msg ("The size of your uploaded thumbnail must be 343*240 size!" "); return false; }                        }                        returnFlag;                }); }, Done:function(res) {// upload Successful callback method $ ("#xcCoverUrl"). Val (Res.data); $("#xcCoverUrlShow"). attr ("src", Res.fastdfshost +res.data); Layer.closeall (' Loading ');        }            }); });

Layui file type and size before upload callback