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Node.js Best Practice Exception Handling
var divide = function(x,y,next) {
// if error condition?
if ( y === 0 ) {
// "throw" the error safely by calling the completion callback
// with the first argument being the error
var err = new Error("Can't divide by zero");
next(err);
}
else {
// no error occured, continue on
next(null, x/y);
}
};
divide(4,2,function(err,result){
// did an error occur?
if ( err ) {
// handle the error safely
console.log('4/2=err', err);
}
else {
// no error occured, continue on
console.log('4/2='+result);
}
});
divide(4,0,function(err,result){
// did an error occur?
if ( err ) {
// handle the error safely
console.log('4/0=err', err);
}
else {
// no error occured, continue on
console.log('4/0='+result);
}
});
var d = require('domain').create();
d.on('error', function(err){
// handle the error safely
console.log(err);
});
// catch the uncaught errors in this asynchronous or synchronous code block
d.run(function(){
// the asynchronous or synchronous code that we want to catch thrown errors on
var err = new Error('example');
throw err;
});
// Definite our Divider Event Emitter
var events = require('events');
var Divider = function(){
events.EventEmitter.call(this);
}; require('util').inherits(Divider, events.EventEmitter);
// Add the divide function
Divider.prototype.divide = function(x,y){
// if error condition?
if ( y === 0 ) {
// "throw" the error safely by emitting it
var err = new Error("Can't divide by zero");
this.emit('error', err);
}
else {
// no error occured, continue on
this.emit('divided', x, y, x/y);
}
// Chain
return this;
};
// Create our divider and listen for errors
var divider = new Divider();
divider.on('error', function(err){
// handle the error safely
console.log(err);
});
divider.on('divided', function(x,y,result){
console.log(x+'/'+y+'='+result);
});
// Divide
divider.divide(4,2).divide(4,0);
/* Outputs:
4/2=2
[Error: Can't divide by zero]
*/
// Define divider as a syncrhonous function
var divideSync = function(x,y) {
// Prepare
var result;
// if error condition?
if ( y === 0 ) {
// "throw" the error safely by returning it
result = new Error("Can't divide by zero");
}
else {
// no error occured, continue on
result = x/y;
}
// Return
return result;
};
// Divide 4/2
var result;
result = divideSync(4,2);
// did an error occur?
if ( result instanceof Error ) {
// handle the error safely
console.log('4/2=err', result);
}
else {
// no error occured, continue on
console.log('4/2='+result);
}
// Divide 4/0
result = divideSync(4,0);
// did an error occur?
if ( result instanceof Error ) {
// handle the error safely
console.log('4/0=err', result);
}
else {
// no error occured, continue on
console.log('4/0='+result);
}
// catch the uncaught errors in this synchronous code block
// try catch statements only work on synchronous code
try {
// the synchronous code that we want to catch thrown errors on
var err = new Error('example');
throw err;
} catch (err) {
// handle the error safely
console.log(err);
}
// catch the uncaught errors that weren't wrapped in a domain or try catch statement
// do not use this in modules, but only in applications, as otherwise we could have multiple of these bound
process.on('uncaughtException', function(err) {
// handle the error safely
console.log(err);
});
// the asynchronous or synchronous code that we want to catch thrown errors on
var err = new Error('example');
throw err;

geekiam commented Mar 29, 2015

Cool, thx!
But what about browsers? What are the best practice to handle error in the browser?

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