How to do DRY error handling in node.js? -

How to do DRY error handling in node.js? -

i have noted in several node.js examples, functions start with:

if (err) { throw err; }

that gets quite repetitive lots of functions.

considering simple script global exception hander. example, in sequence of filesystem operations, such as:

function workonfile2(err,data){ if (err) throw err; fs.readfile('file3', ...) } function workonfile1(err,data){ if (err) throw err; fs.readfile('file2', workonfile2) } function start(){ fs.readfile('file1', workonfile1) }

how should errors handled without repeating oneself?

if line in question coming first line in callback function, can create callback shim work you:

function cbshim(fn) { homecoming function(err) { if (err) { throw err; } homecoming fn.apply(this, arguments); } }

then, instead of passing callback function, pass cbshim(yourcallback) , if first argument passed callback truthy, throw error.

so, in example, instead of this:

function workonfile2(err,data){ if (err) throw err; fs.readfile('file3', ...) } function workonfile1(err,data){ if (err) throw err; fs.readfile('file2', workonfile2) } function start(){ fs.readfile('file1', workonfile1) }

you have this:

function workonfile2(err,data){ fs.readfile('file3', ...) } function workonfile1(err,data){ fs.readfile('file2', cbshim(workonfile2)); } function start(){ fs.readfile('file1', cbshim(workonfile1)); }

or, build own version of readfile() if want throw if returns error.

// own version of readfile throws upon error fs.readfilethrow = function(file, cb) { homecoming fs.readfile(file, function(err, data) { if (err) throw err; homecoming cb(err, data); }); } function workonfile2(err,data){ fs.readfilethrow('file3', ...); } function workonfile1(err,data){ fs.readfilethrow('file2', workonfile2); } function start(){ fs.readfilethrow('file1', workonfile1); }

node.js