Adding missing find function, fixes #564

find is referenced in chapter 8 and is needed for the IO example:

// findParam :: String -> IO Maybe [String]
const findParam = key => map(compose(Maybe.of, find(compose(eq(key), head)), params), url);

Author: dotnetCarpenter

exercises/support.js

@@ -559,7 +559,7 @@ class Task {
   }
 }
 
-// In nodejs the existance of a class method named `inspect` will trigger a deprecation warning
+// In nodejs the existence of a class method named `inspect` will trigger a deprecation warning
 // when passing an instance to `console.log`:
 // `(node:3845) [DEP0079] DeprecationWarning: Custom inspection function on Objects via .inspect() is deprecated`
 // The solution is to alias the existing inspect method with the special inspect symbol exported by node
@@ -724,6 +724,15 @@ const filter = curry(function filter(fn, xs) {
   return xs.filter(fn);
 });
 
+const find = curry(function find(fn, xs) {
+  assert(
+    typeof fn === 'function' && Array.isArray(xs),
+    typeMismatch('(a -> Boolean) -> [a] -> a', [getType(fn), getType(xs), getType(xs)].join(' -> '), 'find'),
+  );
+
+  return xs.find(fn);
+});
+
 const flip = curry(function flip(fn, a, b) {
   assert(
     typeof fn === 'function',
@@ -1071,6 +1080,7 @@ if (typeof module === 'object') {
     concat,
     eq,
     filter,
+    find,
     flip,
     forEach,
     head,