nodegit/promise

The "promise" library gives JavaScript developers a way to handle asynchronous operations, things like fetching data from a server or reading a file, without getting tangled in nested callbacks. It implements the Promises/A+ specification, which is a standard pattern for representing a value that will be available in the future, either as a successful result or an error. At its core, a promise is an object that starts in a pending state and eventually settles: it gets fulfilled with a value or rejected with a reason. You create one by calling new Promise(fn), where your function receives two tools: resolve (call when the operation succeeds) and reject (call when it fails). You can chain operations with .then() so that each step runs only after the previous one finishes, and .catch() handles errors. The library also provides helpers like Promise.all() to wait on multiple promises at once, and Promise.denodeify() to convert older Node.js callback-style functions into promise-returning ones. This is useful for developers working in JavaScript environments that predate native ES6 Promise support, or who need a few extras beyond what the language gives you out of the box. For example, if you're calling an API that uses callbacks but you want to write cleaner promise-based code, denodeify wraps that API for you. The nodeify method goes the other direction: it lets you expose a promise-based function that still works for users expecting traditional callbacks. There are also variants for specific environments, one for Node.js domains support and one tuned for setImmediate. The project is straightforward and intentionally minimal. The README notes that internals are exposed through underscore-prefixed properties, but warns that relying on those will break your code with each new release. Beyond the standard promise methods, the non-standard additions like .done() are there because they solve real problems the spec doesn't cover. The license is MIT.