fixed ts errors

Author: Laoujin

cli-socks/src/components/Product.vue

@@ -67,7 +67,7 @@ import ProductReview from './ProductReview.vue';
 
 export default class Product extends Vue {
   @Prop({default: false}) private premium!: boolean;
-  @Prop() private cartLength: number;
+  @Prop() private cartLength!: number;
 
   product = {
     name: "Vue Socks",
@@ -91,7 +91,12 @@ export default class Product extends Vue {
     if (!this.product.reviews.length) {
       return null;
     }
-    return Math.round(this.product.reviews.map(x => x.rating).reduce((a, c) => a + c, 0) / this.product.reviews.length);
+    const reviews = this.product.reviews as any;
+    const totalStars = reviews
+      .map((x: any) => x.rating)
+      .reduce((a: any, c: any) => a + c, 0);
+
+    return Math.round(totalStars / this.product.reviews.length);
   }
 
   get title() {