# Question 14

### Question

How would you check if a value is a promise in JavaScript?

### Answer

Here's how you can determine if a value is a Promise in JavaScript:

```javascript
function isPromise(value) {
  return typeof value === 'object' && value !== null && 
         typeof value.then === 'function';
}
```

**Explanation:**

1. **`typeof value === 'object' && value !== null`**: This part ensures we're dealing with an object, not a primitive type like a number or string. It also excludes `null`.
2. **`typeof value.then === 'function'`**: The key check! Promises have a `.then()` method that is used to handle their resolution or rejection. If this method exists and is a function, we've likely found a Promise.

**Important Notes:**

* This method works reliably for standard Promises created with `new Promise()`.
* Some libraries might implement custom Promise-like objects. The above check should catch most common cases, but it might not cover every edge case.