Enforce best practices for JavaScript promises.
Ensure that each time a then()
is applied to a promise, a
catch()
is applied as well. Exceptions are made if you are
returning that promise.
Formerly called always-catch
.
myPromise.then(doSomething).catch(errors);
myPromise.then(doSomething).then(doSomethingElse).catch(errors);
function doSomethingElse() { return myPromise.then(doSomething) }
myPromise.then(doSomething);
myPromise.then(doSomething, catchErrors); // catch() may be a little better
function doSomethingElse() { myPromise.then(doSomething) }
You can pass an { allowThen: true }
as an option to this rule
to allow for .then(null, fn)
to be used instead of catch()
at
the end of the promise chain.
Ensure that inside a then()
you make sure to return
a new promise or value.
See http://pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html (rule #5)
for more info on why that's a good idea.
myPromise.then((val) => val * 2));
myPromise.then(function(val) { return val * 2; });
myPromise.then(doSomething); // could be either
myPromise.then(function(val) {});
myPromise.then(() => { doSomething(); });
Enforce standard parameter names for Promise constructors
new Promise(function (resolve) { ... })
new Promise(function (resolve, reject) { ... })
new Promise(function (reject, resolve) { ... }) // incorrect order
new Promise(function (ok, fail) { ... }) // non-standard parameter names
Ensures that new Promise()
is instantiated with the parameter names resolve, reject
to avoid confusion with order such as reject, resolve
. The Promise constructor uses the RevealingConstructor pattern. Using the same parameter names as the language specification makes code more uniform and easier to understand.
You'll first need to install ESLint:
$ npm i eslint --save-dev
Next, install eslint-plugin-promise
:
$ npm install eslint-plugin-promise --save-dev
Note: If you installed ESLint globally (using the -g
flag) then you must also install eslint-plugin-promise
globally.
Add promise
to the plugins section of your .eslintrc
configuration file. You can omit the eslint-plugin-
prefix:
{
"plugins": [
"promise"
]
}
Then configure the rules you want to use under the rules section.
{
"rules": {
"promise/param-names": 2,
"promise/always-return": 2,
"promise/always-catch": 2, // deprecated
"promise/catch-or-return": 2,
}
}
- (c) MMXV jden jason@denizac.org - ISC license.
- (c) 2016 Jamund Ferguson jamund@gmail.com - ISC license.