valid-params.md

Ensures the proper number of arguments are passed to Promise functions (valid-params)

Calling a Promise function with the incorrect number of arguments can lead to unexpected behavior or hard to spot bugs.

Rule Details

This rule is aimed at flagging instances where a Promise function is called with the improper number of arguments.

Examples of incorrect code for this rule:

• Promise.all() is called with 0 or 2+ arguments
• Promise.race() is called with 0 or 2+ arguments
• Promise.resolve() is called with 2+ arguments
• Promise.reject() is called with 2+ arguments
• Promise.then() is called with 0 or 3+ arguments
• Promise.catch() is called with 0 or 2+ arguments
• Promise.finally() is called with 0 or 2+ arguments

Examples of correct code for this rule:

// Promise.all() requires 1 argument
Promise.all([p1, p2, p3])
Promise.all(iterable)

// Promise.race() requires 1 argument
Promise.race([p1, p2, p3])
Promise.race(iterable)

// Promise.resolve() requires 0 or 1 arguments
Promise.resolve()
Promise.resolve({})
Promise.resolve([1, 2, 3])
Promise.resolve(referenceToObject)

// Promise.reject() requires 0 or 1 arguments
Promise.reject()
Promise.reject(Error())
Promise.reject(referenceToError)

// Promise.then() requires 1 or 2 arguments
somePromise().then(value => doSomething(value))
somePromise().then(successCallback, errorCallback)

// Promise.catch() requires 1 argument
somePromise().catch(error => {
  handleError(error)
})
somePromise().catch(console.error)

// Promise.finally() requires 1 argument
somePromise().finally(() => {
  console.log('done!')
})
somePromise().finally(console.log)

When Not To Use It

If you do not want to be notified when passing an invalid number of arguments to a Promise function (for example, when using a typechecker like Flow), you can safely disable this rule.