Reading Node.js assert's module documentation I have been failing to understand what is the meaning of the message parameter and how should I use it.
If I write an assertion like:
assert(container.search('asd') === undefined, "Can't find [asd]");
When runnning the code, if it fails, I just get an exception at the assertion line, and can't see the message:
assert.js:86
throw new assert.AssertionError({
^
AssertionError: false == true
at Object.<anonymous> (c:\tests\Container.js:70:1)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Function.Module.runMain (module.js:501:10)
at startup (node.js:129:16)
at node.js:814:3
The message argument simply defines what the error message will be if the test fails. This is common across most assertion libraries.
Example:
assert(false, 'hello world')
throws the error
AssertionError: hello world
Related
Hello (I am very new to programming!)
I keep getting this error message (below) whenever I try to run my bot in CMD.
(Scroll down for code and error and stuff) I am super confused about all of this!
I tried fixing it by removing the ; but that didn't work, it told me the ) was unexpected, but when I removed the ) it told me it was needed!
Code Block One:
// Runs on bot start
bot.on('ready', () => {
// Now we post into the console that the bot has been turned on.
console.log('Bot turned on in the CMD')
});
Code Block Two: (Semi-Colon Removed)
// Runs on bot start
bot.on('ready', () => {
// Now we post into the console that the bot has been turned on.
console.log('Bot turned on in the CMD')
})
Code Block Three:
bot.on('ready', () => {
// Now we post into the console that the bot has been turned on.
console.log('Bot turned on in the CMD')
}
Expected Result:
Bot turns on, sends a message in the CMD to that effect.
Error #1 (See code block 1 to find the code)
`C:\Users\xgoul\OneDrive\Desktop\Discord Bot\app.js:74
});
^
SyntaxError: Unexpected end of input
at Module._compile (internal/modules/cjs/loader.js:723:23)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
at Module.load (internal/modules/cjs/loader.js:653:32)
at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
at Function.Module._load (internal/modules/cjs/loader.js:585:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
at startup (internal/bootstrap/node.js:283:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)`
Error #2 (See code block 2 to find the code)
`C:\Users\xgoul\OneDrive\Desktop\Discord Bot\app.js:74
})
^
SyntaxError: Unexpected end of input
at Module._compile (internal/modules/cjs/loader.js:723:23)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
at Module.load (internal/modules/cjs/loader.js:653:32)
at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
at Function.Module._load (internal/modules/cjs/loader.js:585:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
at startup (internal/bootstrap/node.js:283:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)`
Error #3 (See code block 3 to find the code)
`C:\Users\XXXX\OneDrive\Desktop\Discord Bot\app.js:74
}
^
SyntaxError: missing ) after argument list
at Module._compile (internal/modules/cjs/loader.js:723:23)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
at Module.load (internal/modules/cjs/loader.js:653:32)
at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
at Function.Module._load (internal/modules/cjs/loader.js:585:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
at startup (internal/bootstrap/node.js:283:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)`
Code block 1 is correct, its returning unexpected end of input because you have to include a return statement.
// Runs on bot start
bot.on('ready', () => {
// Now we post into the console that the bot has been turned on.
console.log('Bot turned on in the CMD');
return('whatever');
});
I'm trying to write a little test of realm-js using node.js console, but after insertion of te first string I see an exception:
> var Realm = require('realm')
TypeError: utf8 is not a function
at Function.from (native)
at Function.from (native)
at module.exports (/home/hermann/node_modules/realm/lib/submit-analytics.js:92:60)
at Object.<anonymous> (/home/hermann/node_modules/realm/lib/index.js:70:42)
at Module._compile (module.js:410:26)
at Object.Module._extensions..js (module.js:417:10)
at Module.load (module.js:344:32)
at Function.Module._load (module.js:301:12)
at Module.require (module.js:354:17)
at require (internal/module.js:12:17)
Anybody can help me with this problem?
UPD. An error occures in realm/lib/submit-analytics.js in this call:
request(`https://api.mixpanel.com/track/?data=${Buffer.from(JSON.stringify(payload), 'utf8').toString('base64')}&ip=1`,
() => { /* Analytics failed. Do nothing. */ });
That's a bug, you must be using Node.js 4.x? I've created an issue to track this -- for now you can just comment out that entire line to make it work for you.
This question is not the same as Extended Errors do not have message or stack trace, which deals with es6 extends, but I'm using es5.
Here's my code
test.js
function FooError(message) {
this.stack = (new Error(message)).stack;
console.log('this.stack', this.stack);
console.log('new_error_stack', (new Error(message)).stack);
console.log('after');
}
FooError.prototype = new Error;
throw new FooError("foo");
This gives the following output : with node version 6.4 (node test.js)
this.stack Error
at Object.<anonymous> (/tmp/test.js:7:22)
at Module._compile (module.js:556:32)
at Object.Module._extensions..js (module.js:565:10)
at Module.load (module.js:473:32)
at tryModuleLoad (module.js:432:12)
at Function.Module._load (module.js:424:3)
at Module.runMain (module.js:590:10)
at run (bootstrap_node.js:394:7)
at startup (bootstrap_node.js:149:9)
at bootstrap_node.js:509:3
new_error_stack Error: foo
at Error.FooError (/tmp/test.js:4:33)
at Object.<anonymous> (/tmp/test.js:9:7)
at Module._compile (module.js:556:32)
at Object.Module._extensions..js (module.js:565:10)
at Module.load (module.js:473:32)
at tryModuleLoad (module.js:432:12)
at Function.Module._load (module.js:424:3)
at Module.runMain (module.js:590:10)
at run (bootstrap_node.js:394:7)
at startup (bootstrap_node.js:149:9)
after
/tmp/test.js:9
throw new FooError("foo");
^
Error
at Object.<anonymous> (/tmp/test.js:7:22)
at Module._compile (module.js:556:32)
at Object.Module._extensions..js (module.js:565:10)
at Module.load (module.js:473:32)
at tryModuleLoad (module.js:432:12)
at Function.Module._load (module.js:424:3)
at Module.runMain (module.js:590:10)
at run (bootstrap_node.js:394:7)
at startup (bootstrap_node.js:149:9)
at bootstrap_node.js:509:3
as you can see, the 'this.stack' doesn't show the same thing at all than the 'new_error_stack', eg, the this.stack shows the stack as if the error was thrown when the require was called. Also, the thrown stack is also "incorrect".
I took the code from https://stackoverflow.com/a/5251506/1993501 , and since I want to use instanceof FooError, I use the line FooError.prototype = new Error.
As you can see, the 'new_error_stack' gives the expected output, but I would have expected both values to be equal.
This has the effect that errors are not very useful for users of my library, see corresponding issue : https://github.com/open-xml-templating/docxtemplater/issues/245
What exactly is happening, and how can I prevent it and keep proper error types (eg being able to use instanceof) ?
I found a possible solution to your problem, but I'm not entirely sure it fixes all of your issues. I'm using Error.prototype instead of new Error (which is what you had). I found this solution from the first answer provided to this question: How do I create a custom Error in JavaScript?
I also changed your console.log lines to concatenate the two strings, as I was using alert() to display the output for testing purposes.
Kevin Hakanson goes over why you may or may not want to go with this solution in his answer. Here's the code to answer your question:
function FooError(message) {
this.stack = (new Error(message)).stack;
console.log('this.stack ' + this.stack);
console.log('new_error_stack ' + (new Error(message)).stack);
console.log('after');
}
FooError.prototype = Error.prototype;
throw new FooError("foo");
You may want to use a try/catch block with that last line.
In Node.js, if I have a method that throws an exception, console.log statements from that method don't fire. I recognize that in the simple test case below that I should catch the exception from the readFileSync call, or otherwise be defensive about it. Just curious if someone could explain the behavior to me.
Simple test case:
var fs = require('fs');
function readAFileThatDoesntExist(filename) {
console.log(filename);
fs.readFileSync(filename);
}
console.log("We're about to read a file that doesn't exist!");
readAFileThatDoesntExist("afile");
Output:
$ node test.js
We're about to read a file that doesn't exist!
fs.js:338
return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
^
Error: ENOENT, no such file or directory 'C:\blog\projects\bloggen\scripts\afile'
at Object.fs.openSync (fs.js:338:18)
at Object.fs.readFileSync (fs.js:182:15)
at readAFileThatDoesntExist (C:\blog\projects\bloggen\scripts\test.js:5:8)
at Object.<anonymous> (C:\blog\projects\bloggen\scripts\test.js:9:1)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:492:10)
at process.startup.processNextTick.process._tickCallback (node.js:244:9)
Ah, figured it out.
It seems that console.log isn't finishing before the process exits... If I use console.warn, the message does show up.
This post explains it: is node.js' console.log asynchronous?
Also, I'm on an older version (0.8.15), so this may no longer be relevant.
I'm trying to catch the stack trace of an node.js uncaughtException and it works fine for different errors but not for throw() statements:
Correct stack trace on exception handling:
$ cat errorFunc.js
process.on('uncaughtException', function(exception) {
console.log('uncaughtException occurred: ' + exception.stack);
});
MyError();
$ node errorFunc.js
uncaughtException occurred: ReferenceError: MyError is not defined
at Object.<anonymous> (/home/jolcese/code/WebEnclaves/Server/errorFunc.js:5:1)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:901:3
$
Missing stack trace on exception caused by throw():
$ cat errorThrow.js
process.on('uncaughtException', function(exception) {
console.log('uncaughtException occurred: ' + exception.stack);
});
throw('my error');
$ node errorThrow.js
uncaughtException occurred: undefined
$
Any idea why?
Thanks
Jose
Disclaimer: I know that using process.on('uncaughtException') is a very, very bad thing and I will be punished but using domains is not an option in this code.
JavaScript lets you throw anything.
If you want to throw errors with stack traces in JavaScript, you need to throw Error objects.
(specification )
Also, throw is an operator and not a function.
Try
throw new Error('my error');
See the manual on Mozilla Developer Network for more information.