Avoid confusing prototype methods for static methods

Correct: `Array.from()` (it’s a static method)
Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method)

This patch uses the common `#` syntax to denote `.prototype.`.

snippets/invertKeyValues.md

@@ -2,7 +2,7 @@
 
 Inverts the key-value pairs of an object, without mutating it. The corresponding inverted value of each inverted key is an array of keys responsible for generating the inverted value. If a function is supplied, it is applied to each inverted key.
 
-Use `Object.keys()` and `Array.reduce()` to invert the key-value pairs of an object and apply the function provided (if any).
+Use `Object.keys()` and `Array.prototype.reduce()` to invert the key-value pairs of an object and apply the function provided (if any).
 Omit the second argument, `fn`, to get the inverted keys without applying a function to them.
 
 ```js