Items not being saved to localStorage

Question

It would appear that the onSubmit function below is saving to localStorage but I deployed the code to the Web and when I refreshed the page, the shopping cart got emptied. I can't test the code after every modification because I'm in development mode and the page re-compiles when it's refreshed but I can test it with the deleteItem function which uses splice. Splice only works on an array and when I click the delete button, the product gets cleared so that tells me it's not using localStorage.

In the component:

items = [];

public onSubmit(thumbnail, quantity, product_name, product_price){

const data = {
thumbnail,
quantity,
product_name,
product_price
};

localStorage.setItem('items', JSON.stringify(data));
this.items.push(JSON.parse(localStorage.getItem('items')));
this.isSubmitted = true;
}

deleteItem(i){
this.items.splice(i,1);

}

In the HTML:

<tr *ngFor="let item of items; let i = index">
<td>
<button type="button" (click)="deleteItem(i)">X</button></td>
<td><img src="{{item.thumbnail}}" /></td>
<td>{{item.quantity}} </td>
<td>{{item.product_name }} </td>
<td>{{item.product_price }} </td>
<td>{{item.quantity * item.product_price }}</td>
</tr>