refactor(MultiSelect): improve container option handling

Author: mrholek

js/src/multi-select.js

@@ -635,7 +635,7 @@ class MultiSelect extends BaseComponent {
 
     const { container } = this._config
     if (container) {
-      getElement(container).append(dropdownDiv)
+      container.append(dropdownDiv)
     } else {
       this._clone.append(dropdownDiv)
     }
@@ -994,6 +994,18 @@ class MultiSelect extends BaseComponent {
     getNextActiveElement(items, target, key === ARROW_DOWN_KEY, !items.includes(target)).focus()
   }
 
+  _configAfterMerge(config) {
+    if (config.container === true) {
+      config.container = document.body
+    }
+
+    if (typeof config.container === 'object' || typeof config.container === 'string') {
+      config.container = getElement(config.container)
+    }
+
+    return config
+  }
+
   // Static
 
   static multiSelectInterface(element, config) {