Code only works when page is reloaded

The following code only works when I force it to reload at the end. How can I get the code to run without forcing it to reload?

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

this.product_price = parseFloat(product_price);

var data = {
this.isSubmitted = true;

 // Get the saved stringified object from cache
const retrieverObject: string = localStorage.getItem(this.storageKey) || '';
// Parse it to an array, or set to a blank array, if there is no data
const retrieveObject: Array<any> = retrieverObject ? JSON.parse(retrieverObject) : [];
// Find the item from the array
let presentItem = retrieveObject.find(item => === id);
// Update the data, if the item is found
if (presentItem) {
  //this.quantity += quantity;
  // If the stored objects quantity needs to be updated
  presentItem.quantity += quantity;
} else {
  // Else if not found in the saved array, push the new object
// Set the new object to the same key
localStorage.setItem(this.storageKey, JSON.stringify(retrieveObject));

A post was merged into an existing topic: Cannot read property ‘storageKey’ of undefined