feat: added filter() operation

src/operations/filter/index.js

@@ -0,0 +1,42 @@
+const { updateArray } = require('../common');
+
+module.exports = filter;
+
+/**
+ * Filters elements of array-item selected by path using provided predicate
+ * @param {Object | any[]} object object to update
+ * @param {string | string[]} path path to be updated
+ * @param {function} predicate filter predicate
+ * @returns {Object | any[]} updated object
+ * @description one of additional functions to work with array items
+ * @docs
+ * ```js
+ * import { filter } from 'immutable-object-update';
+ *
+ * const state = {
+ *     a: {
+ *         b: [ 1, 2, 3, 4, 5 ]
+ *     }
+ * };
+ * const isOdd = item => item % 2;
+ *
+ * const updated = filter(state, [ 'a', 'b' ], isOdd);
+ *
+ * // or
+ *
+ * const updated = filter(state, 'a.b', isOdd);
+ * ```
+ *
+ * As a result we will receive new object with structure below:
+ *
+ * ```js
+ * {
+ *     a: {
+ *         b: [ 1, 3, 5 ]
+ *     }
+ * }
+ * ```
+ */
+function filter(object, path, predicate) {
+    return updateArray(object, path, array => array.filter(predicate));
+}

src/operations/index.js

@@ -12,6 +12,7 @@ const unshift = require('./unshift');
 const unshiftAll = require('./unshiftAll');
 const insert = require('./insert');
 const insertAll = require('./insertAll');
+const filter = require('./filter');
 
 module.exports = {
     update,
@@ -27,5 +28,6 @@ module.exports = {
     unshift,
     unshiftAll,
     insert,
-    insertAll
+    insertAll,
+    filter
 };