bank - js advanced exam

class Bank {
    constructor(bankName) {
        this._bankName = bankName;
        this.allCustomers = [];
    }

    newCustomer(customer) {
        this.allCustomers.find((c) => {
            if (c.personalId === customer.personalId) {
                throw new Error(
                    `${customer.firstName} ${customer.lastName} is already our customer!`
                );
            }
        });
        //customer.transactionInfos = [];
        //customer.totalMoney = 0;
        this.allCustomers.push(customer);
        return customer;
    }

    depositMoney(personalId, amount) {
        let person = this.allCustomers.find((c) => {
            return c.personalId === personalId;
        });
        if (person === undefined) {
            throw new Error('We have no customer with this ID!');
        } else {
            if (isNaN(person.totalMoney)) {
                person.totalMoney = amount;
            } else {
                person.totalMoney += amount;
            }
            if (!Array.isArray(person.transactionInfos)) {
                person.transactionInfos = [];
            }
            let message = `${person.transactionInfos.length + 1}. ${
                person.firstName
            } ${person.lastName} made deposit of ${amount}$!`;
            person.transactionInfos.push(message);
            return `${person.totalMoney}$`;
        }
    }

    withdrawMoney(personalId, amount) {
        let person = this.allCustomers.find((c) => {
            return c.personalId === personalId;
        });
        if (person === undefined) {
            throw new Error('We have no customer with this ID!');
        } else {
            if (isNaN(person.totalMoney)) {
                person.totalMoney = amount;
            }
            if (!Array.isArray(person.transactionInfos)) {
                person.transactionInfos = [];
            }
            if (person.totalMoney < amount) {
                throw new Error(`${person.firstName} ${person.lastName} does not have enough money to withdraw that amount!`);
            } else {
                person.totalMoney -= amount;

                let message = `${person.transactionInfos.length + 1}. ${
                    person.firstName
                } ${person.lastName} withdrew ${amount}$!`;

                person.transactionInfos.push(message);

                return `${person.totalMoney}$`;
            }
        }
    }

    customerInfo(personalId) {
        let person = this.allCustomers.find((c) => {
            return c.personalId === personalId;
        });
        if (person === undefined) {
            throw new Error('We have no customer with this ID!');
        } else {
            let infoString = '';
            infoString += `Bank name: ${this._bankName}\n`;
            infoString += `Customer name: ${person.firstName} ${person.lastName}\n`;
            infoString += `Customer ID: ${person.personalId}\n`;
            infoString += `Total Money: ${person.totalMoney}$\n`;
            infoString += `Transactions:\n`;
            for (let index = person.transactionInfos.length - 1; index >= 0; index--) {
                infoString += person.transactionInfos[index];
                if (index !== 0) {
                    infoString += `\n`;
                }
            }
            return infoString;
        }
    }
}