I want to create an array that contains objects of Expense class. Everything seems great until I try to use “find” method on my array. Error: “Property ‘find’ does not exist on type ‘Expense[]’.”

class ExpenseTracker {
    private data: Array<Expense>;

    constructor() {
        this.data = [];
    }

    public addExpense(_expense: Expense): void {
        this.data.push(_expense);
    }

    public showExpenses(_id?: number): Expense | Expense[] {
        if (_id) {
            const expense = this.data.find((el) => el.id === _id);
            return expense ? expense : this.data;
        } else {
            return this.data;
        }
    }
}

class Expense {
    id: number;
    name: string;
    amount: number;
    category: string;
    description: string;

    constructor(_id: number, _name: string, _amount: number, _category: string = '', _description: string = '') {
        this.id = _id;
        this.name = _name;
        this.amount = _amount;
        this.category = _category;
        this.description = _description;
    }
}

const expenseTracker = new ExpenseTracker();
const expense1 = new Expense(1, 'Groceries', 5.55);
expenseTracker.addExpense(expense1);
console.log(expenseTracker.showExpenses(1)); // Should show expense with id 1
console.log(expenseTracker.showExpenses()); // Should show all expenses

I googled for answer but didn’t find anything that could solve my problem.