Add includes method #15 (#20)

* Add `includes` method.

* linting

Co-authored-by: thooijenga <[email protected]>

Author: tomhooijenga

README.md

@@ -23,6 +23,7 @@ iterator.new(iterable)
     .find(...)
     .findIndex(...)
     .some(...)
+    .includes(...)
     .intoArray()
     .intoSet()
     .intoMap()

lib/main.js

@@ -87,7 +87,7 @@ export const Iterator = {
     },
 
     /**
-     * Applies the lambda function to each item of the interable.
+     * Applies the lambda function to each item of the iterable.
      *
      * @param  {ForEachCallback} lambda
      */
@@ -197,7 +197,22 @@ export const Iterator = {
     },
 
     /**
-     * Flattens a nested interable structure for n depth.
+     * Determine if the given value is included in the iterable.
+     * Optionally specify a position at which to begin searching.
+     *
+     * @param {*} value
+     * @param {number} [fromIndex=0]
+     *
+     * @return {boolean}
+     */
+    includes(value, fromIndex = 0) {
+        return !!this.find((item, index) => {
+            return item === value && index >= fromIndex;
+        });
+    },
+
+    /**
+     * Flattens a nested iterable structure for n depth.
      *
      * @param  {number} [depth=1]
      *