Node.js writing data to file throws an error - node.js

Question

Got this error when I run my program
TypeError: Callback is not a function
// Update data from a new file
lib.update = function(dir,file,callback){
//Open the file for writing
fs.open(lib.baseDir+dir+'/'+'.json','r+',function(err,fileDescriptor){
if(!err && fileDescriptor){
var stringData= JSON.stringify(data);
//Truncate the file before writing
fs.truncate(fileDescriptor,function(err){
if(!err){
//Write to the file and close it
fs.writeFile(fileDescriptor,stringData,function(err){
if(!err){
fs.close(fileDescriptor,function(err){
if(!err){
callback(false);
}else {
callback('Error closing existing file!')
}
})
}else {
callback('Error writing to existing file')
}
});
}else {
callback('Error Truncating file')
}
});
}else {
callback('Could not open file for updating! May not exist yet')
}
});
}

Answer 1

I propose you to refactor your code to be a little more clear about what you are doing. Something like this, it will help you find where errors come. Using promises better than use a lot of callbacks.
Just my contribution.
lib.update = function(dir, file, data) {
const updateP = new CustomPromise();
openFile()
.then(truncateFile)
.then(writeFile.bind(this, JSON.stringify(data)))
.then(closeFile)
.then(updateP.resolve) // at this point all the functions was successful
.catch((errorType) =>
errorType !== ERROR_TYPE.ERROR_CLOSING_FILE // something fail try to close the file
? closeFile().finally(() => updateP.reject(errorType))
: updateP.reject(errorType),
);
return updateP.promise;
};
// Constants
const ERROR_TYPE = Object.freeze({
ERROR_OPEN_FILE: 'error-open-file',
ERROR_TRUNCATING_FILE: 'error-truncating-file',
ERROR_WRITING_FILE: 'error-writing-file',
ERROR_CLOSING_FILE: 'error-closing-file',
});
// Private functions
function CustomPromise() {
this.promise = new Promise(function(resolve, reject) {
this.resolve = resolve;
this.reject = reject;
});
}
function openFile() {
const openP = new CustomPromise();
fs.open(lib.baseDir + dir + '/' + '.json', 'r+', function(err, fileDescriptor) {
(err || !fileDescriptor) && openP.reject(ERROR_TYPE.ERROR_OPEN_FILE);
openP.resolve(fileDescriptor);
});
return openP.promise;
}
function truncateFile(fileDescriptor) {
const truncateP = new CustomPromise();
fs.truncate(fileDescriptor, function(err) {
err && truncateP.reject(ERROR_TYPE.ERROR_TRUNCATING_FILE);
truncateP.resolve(fileDescriptor);
});
return truncateP.promise;
}
function writeFile(data, fileDescriptor) {
const writeFileP = new CustomPromise();
fs.writeFile(fileDescriptor, data, function(err) {
err && writeFileP.reject(ERROR_TYPE.ERROR_WRITING_FILE);
writeFileP.resolve(fileDescriptor);
});
return writeFileP.promise;
}
function closeFile(fileDescriptor) {
const closeP = new CustomPromise();
fs.close(fileDescriptor, function(err) {
err && closeP.reject(ERROR_TYPE.ERROR_CLOSING_FILE);
closeP.resolve();
});
return closeP.promise;
}