In my NodeJS program, I parse some user JSON file.
So I use :
this.config = JSON.parse(fs.readFileSync(path));
The problem is that if the json file is not correctly formated, the error thrown is like:
undefined:55
},
^
SyntaxError: Unexpected token }
at Object.parse (native)
at new MyApp (/path/to/docker/lib/node_modules/myApp/lib/my-app.js:30:28)
...
As it is not really user friendly I would like to throw an Error specifying some user friendly message (like "your config file is not well formated") but I want to keep the stacktrace in order to point to the problematic line.
In the Java world I used throw new Exception("My user friendly message", catchedException) in order to have the original exception which caused that one.
How is it possible in the JS world?
Use a try / catch block:
try {
this.config = JSON.parse("}}junkJSON}");
//...etc
}
catch (e) {
//console.log(e.message);//the original error message
e.message = "Your config file is not well formatted.";//replace with new custom message
console.error(e);//raise the exception in the console
//or re-throw it without catching
throw e;
}
http://jsfiddle.net/0ogf1jxs/5/
UPDATE: If you really feel the need for a custom error you can define your own:
function BadConfig(message) {
this.message = message;
this.name = "BadConfig";
}
BadConfig.prototype = new Error();
BadConfig.prototype.constructor = BadConfig;
try {
this.config = JSON.parse("}}badJson}");
} catch(e) {
throw new BadConfig("Your JSON is wack!");
}
Lots of useful info at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error
try {
this.config = JSON.parse(fs.readFileSync(path));
} catch (e) {
throw new Error("User friendly message");
}