feat(storage): try to preset cart data from storage

src/index.js

@@ -7,7 +7,7 @@
 import { _config } from '@ecomplus/utils'
 
 /**
- * JS lib to handle products search with E-Com Plus stores.
+ * Vanilla JS library to handle shopping cart object on E-Com Plus stores.
  * @module @ecomplus/shopping-cart
  * @see EcomCart
  *
@@ -28,10 +28,71 @@ const _key = 'ecomShoppingCart'
 const _storage = typeof window === 'object' && window.localStorage
 
 export default function (storeId, storageKey = _key, localStorage = _storage) {
+  const self = this
+
   /**
    * Respective Store ID number.
    * @name EcomCart#storeId
    * @type {number}
    */
   this.storeId = storeId || _config.get('store_id')
+
+  /**
+   * Item key to handle persistent JSON {@link EcomCart#data}
+   * with [localStorage]{@link EcomSearch#localStorage}.
+   * @name EcomCart#storageKey
+   * @type {string|null}
+   */
+  this.storageKey = storageKey
+
+  /**
+   * [Storage interface]{@link https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage}.
+   * @name EcomCart#localStorage
+   * @type {object}
+   */
+  this.localStorage = localStorage
+
+  /**
+   * Shopping cart data object.
+   * @name EcomCart#data
+   * @type {array<string>}
+   */
+  this.data = {}
+
+  if (localStorage && storageKey) {
+    // try to preset cart data from storage
+    const json = localStorage.getItem(storageKey)
+    if (typeof data === 'string') {
+      let data
+      try {
+        data = JSON.parse(json)
+      } catch (e) {
+        // ignore invalid JSON
+      }
+      if (data && Array.isArray(data.items)) {
+        self.data = data
+      }
+    }
+  }
 }
+
+/**
+ * Construct a new shopping cart instance object.
+ * @class EcomCart
+ * @param {number} [storeId=_config.get('store_id')] - Preset Store ID number
+ * @param {string|null} [storageKey='ecomShoppingCart'] - Item key to persist search history data
+ * @param {object} [localStorage=window.localStorage] -
+ * [Local Storage interface]{@link https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage}
+ *
+ * @example
+
+const cart = new EcomCart()
+
+ *
+ * @example
+
+// Defining Store ID other than the configured on `ecomUtils._config`
+const storeId = 2000
+const cart = new EcomCart(storeId)
+
+ */