Cannot read property 'metadata' of null Nodejs - node.js

Question

This is my error:
TypeError: Cannot read property 'metadata' of null
at gfs.files.findOne (M:\FinalProject\Commerce\routes\index.js:187:13)
at result (M:\FinalProject\Commerce\node_modules\mongodb\lib\utils.js:414:17)
This is my code :
router.get('/:filename', (req,res) => {
const img = req.params.filename; // Filename
gfs.files.findOne({filename: img}, (req,file) =>{
if(file.metadata.brand=="Mango"){
const brand = "Mango";
displayOne(brand);
}
else if(file.metadata.brand=="Cocotail")
{
const brand = "Cocotail";
displayOne(brand);
}
else if(file.metadata.brand==null)
{
console.log("Null");
}
function displayOne(brand)
{
gfs.files.find({'metadata.brand': brand }).toArray((err,files)=>{
if(!file || file.length ===0)
{
return res.status(404).json({
err: 'No files exist'
});
}
if(file.contentType === 'image/jpeg' || file.contentType === 'image/png')
{
file.isImage = true;
}
else
{
res.status(404).json({
err: 'Not an image'
});
file.isImage = false;
}
res.render('singleproduct',{
file:file,
relatedProduct:files, // Related Products
isSearch:0
});
});
}
});
});
Please give me any ideas about this error. i couldn't find out what is the major reason for this error. I searched on google but there are no appropriate solutions for that.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Thank you

Answer 1

Did you console what you get just above
(file.metadata.brand=="Mango")
in file? seems you don't get any data from
gfs.files.findOne({filename: img}
try this:
if(file && file.metadata.brand=="Mango"){
const brand = "Mango";
displayOne(brand);
}
else if(file && file.metadata.brand=="Cocotail")
{
const brand = "Cocotail";
displayOne(brand);
}
else if(file && file.metadata.brand==null)
{
console.log("Null");
}
else{
console.log("didinot find value")
}