Question 1

How to check if an object is a promise using is-promise?

Accepted Answer

Import the library and call `isPromise(object)`; it returns true if the object has a `then` method that is a function, false otherwise. For example, `isPromise(Promise.resolve())` returns true, and `isPromise({})` returns false.

Question 2

Is is-promise better than using `instanceof Promise` in JavaScript?

Accepted Answer

is-promise is more reliable for cross-environment compatibility and handles non-native promises that follow Promises/A+, while `instanceof` only works with native promises and can fail in some contexts like iframes or different global scopes.

Question 3

How to install is-promise in a Node.js project?

Accepted Answer

Run `npm install is-promise` to add it as a dependency, then import it in your code with `import isPromise from 'is-promise'` for ES modules or `const isPromise = require('is-promise')` for CommonJS.

Question 4

Does is-promise work with async/await and modern JavaScript?

Accepted Answer

Yes, it can detect promises returned by async functions, but it doesn't directly interact with async/await syntax; it checks the underlying promise objects, so it's compatible with modern asynchronous code.

Question 5

What's the difference between is-promise and libraries like bluebird for promise detection?

Accepted Answer

is-promise is focused solely on detection and is minimal, while bluebird offers enhanced promise features and utilities. Use is-promise when you only need to identify promises without additional functionality.

Question 6

How to use is-promise as a type guard in TypeScript?

Accepted Answer

The library includes TypeScript definitions, so you can use it to narrow types; for instance, `if (isPromise(obj)) { // obj is typed as PromiseLike }` helps ensure type safety in conditional checks.

is-promise

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