how to bind method to variable inside constructor method in class

Question

while I'm retrieving data using getValue() and binding its value to this.itemList variable in the constructor method inside the class it returns an empty array however there are data in local storage how is the right way to do that?.

 class UI { constructor() { this.storageBudget = UI.getValue(this.BUDGET_LOCAL_STORAGE); this.itemList = JSON.parse(UI.getValue(this.EXPENSE_LOCAL_STORAGE)) || []; this.itemID = 0; this.BUDGET_LOCAL_STORAGE = 'BUDGET_LOCAL_STORAGE'; this.EXPENSE_LOCAL_STORAGE = 'EXPENSE_LOCAL_STORAGE'; } static save(key, value) { localStorage.setItem(key, value); } static getValue(key) { return localStorage.getItem(key); } }

Answer 1

You're using this.BUDGET_LOCAL_STORAGE and this.EXPENSE_LOCAL_STORAGE in the calls to UI.getValue() before you set them. So set those properties before you try to use them.

 class UI { constructor() { this.BUDGET_LOCAL_STORAGE = 'BUDGET_LOCAL_STORAGE'; this.EXPENSE_LOCAL_STORAGE = 'EXPENSE_LOCAL_STORAGE'; this.storageBudget = UI.getValue(this.BUDGET_LOCAL_STORAGE); this.itemList = JSON.parse(UI.getValue(this.EXPENSE_LOCAL_STORAGE)) || []; this.itemID = 0; } static save(key, value) { localStorage.setItem(key, value); } static getValue(key) { return localStorage.getItem(key); } }