为什么这个 if 语句不起作用？

Question

I am relatively new to development and am unfamiliar with lingo or how to properly ask questions. I am attempting to create a put request to update a profile image using express-fileupload. If I don't include the fist if statement, console returns null and nothing renders or saves. As is, the app crashes. I'm hoping simply posting the code here will suffice for someone to see what the issue is. Thanks ahead of time for helping a newbie.

router.put("/artistsbe/:id", middleware.isLoggedIn, function(req, res){
Artists.findByIdAndUpdate(req.params.id, req.body, function(err, artist){
    if(req.files != "null"){
        let image = req.files.artistImage;
        image.mv("./public/images/" + req.files.artistImage.name, function(err){
            if(err){
                console.log(err);
            }
        });
    } else {
        res.redirect("back");
    }
});

});

Answer 1

I think you just need to do:

if(req.files) {

This will evaluate as truthy if files is not undefined null false or other falsey values.

Answer 2

The problem you have is that you are comparing req.files to a string "null" . Instead, you should compare against the type null .

Also, you may also want to check for undefined . What you can do is write something like this:

if (req.files) {... }

This way, you will check if req.files is not null nor undefined (and also false , but I don't think this variable should receive a boolean value, but you never know...)

Hope my answer was helpful

Answer 3

Try this

router.put("/artistsbe/:id", middleware.isLoggedIn, function(req, res){
Artists.findByIdAndUpdate(req.params.id, req.body, function(err, artist){
if(req.files){
    let image = req.files.artistImage;
    image.mv("./public/images/" + req.files.artistImage.name, function(err){
        if(err){
            console.log(err);
        }
    });
} else {
    res.redirect("back");
}
});

});