feat: use 'DOCUMENT' of '@angular/common' instead of 'document' of window

Author: damingerdai

src/app/containers/default-layout/default-layout.component.ts

@@ -1,6 +1,8 @@
-import {Component, OnDestroy} from '@angular/core';
+import {Component, OnDestroy, Inject} from '@angular/core';
+import { DOCUMENT } from '@angular/common';
 import { navItems } from './../../_nav';
 
+
 @Component({
   selector: 'app-dashboard',
   templateUrl: './default-layout.component.html'
@@ -9,17 +11,19 @@ export class DefaultLayoutComponent implements OnDestroy {
   public navItems = navItems;
   public sidebarMinimized = true;
   private changes: MutationObserver;
-  public element: HTMLElement = document.body;
-  constructor() {
+  public element: HTMLElement ;
+  constructor(@Inject(DOCUMENT) _document?: any) {
 
     this.changes = new MutationObserver((mutations) => {
-      this.sidebarMinimized = document.body.classList.contains('sidebar-minimized');
+      this.sidebarMinimized = _document.body.classList.contains('sidebar-minimized');
     });
 
     this.changes.observe(<Element>this.element, {
       attributes: true,
       attributeFilter: [ 'class' ]
     });
+
+    this.element = _document.body;
   }
 
   ngOnDestroy(): void {