A collection of utilities for working with JavaScript/TypeScript errors.
npm install @mvf4z7/errors
An error class that can be used to wrap an existing error object with a new one. The new error has it's own error message, but the stack trace is composed of the newly created error and the wrapped error.
const error = new Error('message');
const wrappedError = new WrappedError('Additional message', error);
A reference to the original error that was wrapped.
const error = new Error('message');
const wrappedError = new WrappedError('additional message', error);
wrappedError.causedBy === error; // true
Because WrappedError
extends the built in Error
class, a WrappedError
instance stores a stack trace that can be referenced through the stack
property. A WrappedError
's stack trace is composed of the stack trace of the WrappedError
's own stack trace, as well as the stack trace of the error that was was wrapped.
function fetchUsers() {
throw new Error('Network error!');
}
try {
try {
fetchUsers();
} catch (error) {
throw new WrappedError('Failed to fetch users', error);
}
} catch (error) {
console.log(error.stack);
/* error.stack value
WrappedError: Failed to fetch users
at Object.<anonymous> (/Users/john-doe/Code/errors-test/index.js:11:11)
at Module._compile (internal/modules/cjs/loader.js:1068:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1097:10)
at Module.load (internal/modules/cjs/loader.js:933:32)
at Function.Module._load (internal/modules/cjs/loader.js:774:14)
at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
at internal/main/run_main_module.js:17:47
Caused by: Error: Network error!
at fetchUsers (/Users/john-doe/Code/errors-test/index.js:4:9)
at Object.<anonymous> (/Users/john-doe/Code/errors-test/index.js:9:5)
at Module._compile (internal/modules/cjs/loader.js:1068:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1097:10)
at Module.load (internal/modules/cjs/loader.js:933:32)
at Function.Module._load (internal/modules/cjs/loader.js:774:14)
at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
at internal/main/run_main_module.js:17:47
*/
}
A shorthand function for creating an instance of WrappedError
. See the WrappedError
docs for more details on the returned error object.
try {
const id = 123;
getFooById(id);
} catch (error) {
throw Errors.wrap(`Failed to get Foo with ID ${id}.`, error);
}
Tests if the provided error object is an instance of the provided error class or wraps an error of the provided error class. If the provided error object is an instance of the WrappedError
class or another class that extends WrappedError
, the errors causeBy
property will be recursively checked for instances of the provided error class.
class CustomError extends Error {
constructor() {
super('A meaningful error message');
this.name = 'CustomError';
}
}
const customError = new CustomerError();
const wrappedError = Errors.wrap('Additional error message', customError);
Errors.wraps(customError, CustomError); // true
Errors.wraps(wrappedError, CustomError); // true
Errors.wraps(customError, TypeError); // false
Errors.wraps(wrappedError, TypeError); // false
If the provided error object is an instance of WrappedError
then the error's causedBy
property is unwrapped recursively until an instance of ErrorClass
is found, at which time it is returned. If the provided error is not an instance of WrappedError
, the error will be returned if it is an instance of ErrorClass
.
In either scenario, if an instance of ErrorClass
is not found then null
is returned.
class CustomError extends Error {
constructor() {
super('A meaningful error message');
this.name = 'CustomError';
}
}
const customError = new CustomError();
const wrapped = Errors.wrap('Additional error message', customError);
const wrappedTwice = Errors.wrap(
'Yet another error message',
wrappedCustomError
);
Errors.unwrap(wrapped, CustomError); // customError
Errors.unwrap(wrappedTwice, CustomError); // customError
Errors.unwrap(customError, CustomError); // customError
Errors.unwrap(wrapped, TypeError); // null
Errors.unwrap(customError, TypeError); // null