Add isNil and isUndefined

snippets/isNil.md

@@ -0,0 +1,14 @@
+### isNil
+
+Returns `true` if the specified value is `null` or `undefined`, `false` otherwise.
+
+Use the strict equality operator to check if the value and of `val` are equal to `null` or `undefined`.
+
+```js
+const isNil = val => val === undefined || val === null;
+```
+
+```js
+isNil(null); // true
+isNil(undefined); // true
+```

snippets/isUndefined.md

@@ -0,0 +1,13 @@
+### isUndefined
+
+Returns `true` if the specified value is `undefined`, `false` otherwise.
+
+Use the strict equality operator to check if the value and of `val` are equal to `undefined`.
+
+```js
+const isUndefined = val => val === undefined;
+```
+
+```js
+isUndefined(undefined); // true
+```

tag_database

@@ -89,6 +89,7 @@ isEven:math
 isFunction:type,function
 isLowerCase:string,utility
 isMap:type
+isNil:type
 isNull:type
 isNumber:type,math
 isObject:type,object
@@ -102,6 +103,7 @@ isString:type,string
 isSymbol:type
 isTravisCI:node
 isTypedArray:type
+isUndefined:type
 isUpperCase:string,utility
 isValidJSON:type,json
 isWeakMap:type