Add isPromise snippet

snippets/isPromise.md

@@ -0,0 +1,16 @@
+### isPromise
+
+Returns `true` if an object looks like a [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise), `false` otherwise.
+
+Check if the object is not `null`, its `typeof` matches either `object` or `function` and if it has a `.then` property, which is also a `function`.
+
+```js
+const isPromise = obj =>
+  obj !== null && (typeof obj === 'object' || typeof obj === 'function') && typeof obj.then === 'function';
+```
+
+```js
+isPromise({then:function () {return ''}}); // true
+isPromise(null); // false
+isPromise({}); // false
+```

tag_database

@@ -73,6 +73,7 @@ isFunction:utility
 isNull:utility
 isNumber:utility
 isPrime:math
+isPromise:utility
 isString:utility
 isSymbol:utility
 JSONToDate:date