Restrictions before JS uploads images include (jpg jpg gif and size, height and width), etc. _javascript skills

function limitImg(){
var img=document. getElementById(arguments[0]);//The object displaying the image
var maxSize=arguments[1];//
var allowGIF=arguments[2]||false;
var maxWidth=arguments[3 ]||0;
var maxHeight=arguments[4]||0;
var postfix=getPostfix(img.src);
var str=".jpg";
if(allowGIF) {str =".gif"}
if(str.indexOf(postfix.toLowerCase())==-1){
if(allowGIF){return "The image format is wrong, only jpg or gif images can be uploaded ";}else{return "The image format is incorrect, only jpg images can be uploaded";}
}else if(img.fileSize>maxSize*1024){
return "The image size exceeds the limit, please limit it to" maxSize "Within K";
}else{
if(img.fileSize==-1){
return "The picture format is wrong. It may be damaged or the extension has been changed. Please choose another picture. ";
}else{
if(maxWidth>0){
if(img.width>maxWidth){
return "The image width exceeds the limit, please keep it within " maxWidth " pixels";
}else{
if(img.height>maxHeight){
return "The image height exceeds the limit, please keep it within " maxHeight "pixels";
}else{
return "" ;
}
}
}else{
return "";
}
}
}
}
//Get the file extension based on the path
function getPostfix(path){
return path.substring(path.lastIndexOf("."),path.length);
}