When using promises in your SuiteScript scripts to implement asynchronous programming, you should consider the following best practices.

If you are using SuiteScript 2.1 scripts, consider using the async and await keywords to implement asynchronous solutions instead of using the promise keyword.

Best practices for coding promises:

• Always use a promise rejection by including a promise.catch handler.
• Do not nest promises. Chain your promises instead. Or use async/await functionality.
• Keep promise chains short to avoid significant overuse of memory and CPU.
• Use promise.finally if you have code that should run regardless of the outcome of the promise.
• Use promise.all for multiple unrelated asynchronous calls.
• Do not define rejection handlers as the second argument for promise.then calls. Instead, use promise.catch.
• If you need to access results of promises running in parallel, use promise.spread.
• To limit concurrency, use promise.map.
• Use promise.then to run code after the promise completes.

Best practices when using async and await keywords:

• Rewrite promise code to use async/await.
• Schedule first, await later.
• Avoid mixing callback-based APIs with promise-based APIs.
• Refrain from using return await.
• Remember that for SuiteScript 2.1 server-side scripts, only a subset of modules support the use of the async and await keywords: N/http, N/https, N/llm, N/query, N/search, and N/transaction.