Do I need to return after early resolve/reject?

javascript

promises

error-handling

code-readability

byAnton Shumikhin·Aug 10, 2024

// An unexpected programming journey starts with a function 
function processData(input) {
  return new Promise((resolve, reject) => {
    if(input.valid) {
      resolve('Processed'); // Voila! All good, let's wrap this up,
      return; // Grab your coat, we are leaving!
    }
    reject('Invalid input'); // Houston, we have a problem  
    // No need for return; it's so bad, we don't want to see what's next
  });
}

Essential Tip: When uneasy lies the function that bears a promise, always use return post-invocation (right after resolve() or reject()) to prevent any further execution of code lurking there beyond your promise.

Promise handling practices: The good, the bad, and the return

Going solo: Promises resolve or reject only once

Recall that a promise can be resolved or rejected just once. An early return ensures this solitary nature of a promise is respected. Ignore early return at your own peril—you might end up attempting to settle the promise multiple times, leading to confusing and hard-to-pin bugs that haunt your code.

Code readability: Keeping it lean and mean with an early return

It’s always a neat trick to flatten your code by using early return in conditional statements. It aids in ushering clarity and prevent unnecessary indentation. So returning right after a resolve() or reject() ensures a similar trend in your promise handling.

Consistency: A subtle art in promise management

An occasional skip of a return after a rejection might not stir up a storm, especially when there are no lines of code afterwards. Your code, however, deserves the immunity from unintended side-effects caused by future code additions. So, bring consistency in promise handling by always including a return.

Mastering exceptions and promise controls

Exception handling in promises: The rescuer we all need

Promises in JavaScript are throw safe. Any exception is turned into a rejection making the promise a reliable candidate for asynchronous error handling. Efficient error handling = fewer sleepless nights.

Synchronous Vs Asynchronous: Know your battles

Promises are perfect for asynchronous operations. No need to force-fit them for synchronous actions. Let's respect the boundaries and utilize promises where it shines the brightest.

Library caveats: Know your tools

When it comes to different libraries, there could be advice for undefined return values after promise rejection to align with their implementations. Better to be aware than sorry.

The maintenance mogul: Early return

Consistent use of return post-promise resolution or rejection boosts code readability and maintainability. Be considerate to your future self and others who might work with your code.

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