added history

src/app/board/board.component.ts

@@ -10,6 +10,7 @@ export class BoardComponent implements OnInit {
   draw: boolean;
   xIsNext: boolean;
   fields: any[];
+  history: any[];
 
   constructor() {}
 
@@ -22,6 +23,7 @@ export class BoardComponent implements OnInit {
     this.draw = false;
     this.xIsNext = true;
     this.fields = Array(9).fill(null);
+    this.history = [];
   }
 
   get player() {
@@ -36,6 +38,8 @@ export class BoardComponent implements OnInit {
     if (!this.fields[i]) {
       this.fields.splice(i, 1, this.player);
 
+      this.history.push(this.fields.slice());
+
       this.xIsNext = !this.xIsNext;
       this.calculateWinner();
     }