Handling errors using Parse.com Cloud Code and javascript API - parse-platform

Question

What is the best way to handle errors using Parse.com Cloud Code. I'm able to use console.log and Firebug to see when Parse Cloud Code throws an error, but I need some help with how to notify the client that something went wrong. Some sample code from both sides would really be great -- Cloud Code and client side javascript code.

Answer 1

I preferred it this way -
On Cloud Code make one ErrorHandler.JS file -
exports.sendError = function(response, message, data) {
console.log("Message - " + message + " Data - " + JSON.stringify(data)); // To print LOG on Cloud Code
// Moreover you can use any of - "console.error/warn" - as mentioned - https://parse.com/docs/cloud_code_guide#logging
response.error({
status : false, // Indicates EXECUTION STATUS - I am using "successHandler" also & using STATUS as "true"
message : message, // Refers to Error Message
data : data || {} // Error Object or your customized Object
});
}
& client side you will have all data to print if you want or you can just show alert message to the Users.
More over it's preferred to check both SERVER side as well as CLIENT side LOG for DEVELOPING purpose because PARSE Cloud Code stores only last 100 messages in LOG.
& In order to implement proper LOGGING you must made some custom procedures with proper storage structure in terms of CLASS.

Answer 2

Parse has a section on Error Handling for Promises.
For instance when running a query in Cloud Code
query.find().then(function(result){ ... },
function(error){
response.error("Error occurred: " + error.message);
}
That will send error message down the client.

Answer 3

As an experiment I tried response.error with various strings/objects, below is what each returned (the commment shows the return value to the client).
Essentially, it always returns code 141, and you can only return a string. I was surprised that passing the proverbial err object from an exception returned {} my guess is this is for security reasons. What I do not understand is why you can't console.log(err) on the server as this has caused me a lot of confusion when trying to figure out what is going on. You basically always need to do err.message in your console.log statements to figure out what's really going on.
response.error("Some String of text") // --> {code: 141, message: "Some String of text"}
response.error( new Error("My Msg") ) // --> {code: 141, message: "{}"}
try {
var x = asdf.blah;
}catch(err) {
return response.error(err.message); // --> {code: 141, message: "asdf is not defined"}
}
response.error( err ); // --> {code: 141, message: "{}"}
response.error( Parse.Error(Parse.Error.VALIDATION_ERROR, "My Text") ); // --> {code: 141, message: "An error has occurred"}