handle-callback-err
Require error handling in callbacks
This rule was deprecated in ESLint v7.0.0. Please use the corresponding rule in eslint-plugin-n.
In Node.js, a common pattern for dealing with asynchronous behavior is called the callback pattern.
This pattern expects an Error object or null as the first argument of the callback.
Forgetting to handle these errors can lead to some really strange behavior in your application.
function loadData (err, data) {
doSomething(); // forgot to handle error
}
Rule Details
This rule expects that when you’re using the callback pattern in Node.js you’ll handle the error.
Options
The rule takes a single string option: the name of the error parameter. The default is "err".
Examples of incorrect code for this rule with the default "err" parameter name:
Open in Playground
/*eslint handle-callback-err: "error"*/
function loadData (err, data) {
doSomething();
}
Examples of correct code for this rule with the default "err" parameter name:
Open in Playground
/*eslint handle-callback-err: "error"*/
function loadData (err, data) {
if (err) {
console.log(err.stack);
}
doSomething();
}
function generateError (err) {
if (err) {}
}
Examples of correct code for this rule with a sample "error" parameter name:
Open in Playground
/*eslint handle-callback-err: ["error", "error"]*/
function loadData (error, data) {
if (error) {
console.log(error.stack);
}
doSomething();
}
regular expression
Sometimes (especially in big projects) the name of the error variable is not consistent across the project, so you need a more flexible configuration to ensure that the rule reports all unhandled errors.
If the configured name of the error variable begins with a ^ it is considered to be a regexp pattern.
- If the option is
"^(err|error|anySpecificError)$", the rule reports unhandled errors where the parameter name can beerr,errororanySpecificError. - If the option is
"^.+Error$", the rule reports unhandled errors where the parameter name ends withError(for example,connectionErrororvalidationErrorwill match). - If the option is
"^.*(e|E)rr", the rule reports unhandled errors where the parameter name matches any string that containserrorErr(for example,err,error,anyError,some_errwill match).
When Not To Use It
There are cases where it may be safe for your application to ignore errors, however only ignore errors if you are confident that some other form of monitoring will help you catch the problem.
Version
This rule was introduced in ESLint v0.4.5.
Further Reading