对象在forEach循环内似乎未定义

Question

错误日志

--- buildTaxData ---
[ TaxData {
    name: '2017-2018 financial year',
    start: '2017-07-01',
    end: '2018-06-30',
    tax: [ [Object], [Object], [Object], [Object], [Object] ] },
  TaxData {
    name: '2018-2019 financial year',
    start: '2018-07-01',
    end: '2019-06-30',
    tax: [ [Object], [Object], [Object], [Object], [Object] ] } ]
--- buildTaxData ---
undefined
(node:9166) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'find' of undefined
    at Util.getTaxData (/var/www/html/test/testme/myob_payslip_new/lib/Util.js:38:29)
    at Employee.buildTaxData (/var/www/html/test/testme/myob_payslip_new/lib/Employee.js:41:28)
    at Employee.getIncomeTax (/var/www/html/test/testme/myob_payslip_new/lib/Employee.js:61:18)
    at Employee.getNetIncome (/var/www/html/test/testme/myob_payslip_new/lib/Employee.js:72:61)
    at EmployeePrint.fillData (/var/www/html/test/testme/myob_payslip_new/lib/EmployeePrint.js:36:24)
    at arr.forEach (/var/www/html/test/testme/myob_payslip_new/lib/EmployeePrint.js:55:12)
    at Array.forEach (<anonymous>)
    at EmployeePrint.print (/var/www/html/test/testme/myob_payslip_new/lib/EmployeePrint.js:53:10)
    at Processor.process (/var/www/html/test/testme/myob_payslip_new/lib/Processor.js:19:33)
    at App.run (/var/www/html/test/testme/myob_payslip_new/index.js:15:22)
(node:9166) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:9166) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

在EmployeePrint.js中

'use strict';

const Cal = require('./Calculator');
const Util = require('./Util');
const GrossIncome = require('./GrossIncome');
const IncomeTax = require('./IncomeTax');
const NetIncome = require('./NetIncome');
const MySuper = require('./MySuper');

let util = new Util();
let cal = new Cal();

class Employee {

    constuctor() {
        this.firstName = null;
        this.lastName = null;
        this.annualSalary = null;
        this.superRate = null;
        this.timePeriod = null;
    }

    getFullName() {
        let res = this.firstName + ' ' + this.lastName;
        return res;
    }

    getTimePeriod() {
        return this.timePeriod;
    }

    buildTaxData(taxObj) {

        // test
        console.log('--- buildTaxData ---');
        console.log(taxObj);

        let startPeriod = util.parseTimePeriod(this.timePeriod)[0] + ' ' + TIME_PERIOD_YEAR;
        let endPeriod = util.parseTimePeriod(this.timePeriod)[1] + ' ' + TIME_PERIOD_YEAR;

        let currTaxObj = util.getTaxData(taxObj, startPeriod, endPeriod);
        let rightTaxSlot = util.getRightTaxSlot(currTaxObj, this.annualSalary);
        let base = rightTaxSlot['base'];
        let edge = rightTaxSlot['edge'];
        let taxRate = rightTaxSlot['rate'];

        let myReturn = {
            base,
            edge,
            taxRate
        }

        return myReturn;
    }

    getGrossIncome() {
        return new GrossIncome(this.annualSalary).calculate();
    }

    getIncomeTax(taxObj) {
        let res = this.buildTaxData(taxObj);
        let incomeTax = new IncomeTax(this.annualSalary, res.base, res.edge, res.taxRate);
        return incomeTax.calculate();   
    }

    getSuper() {
        let mySuper = new MySuper(this.getGrossIncome(), this.superRate);
        return mySuper.calculate();
    }

    getNetIncome() { 
        let netIncome = new NetIncome(this.getGrossIncome(), this.getIncomeTax());
        return netIncome.calculate();
    }

    fillData(item) {
        this.firstName = item.firstName;
        this.lastName = item.lastName;
        this.annualSalary = item.annualSalary;
        this.superRate = cal.percentToNum(item.superRate);
        this.timePeriod = item.timePeriod;

        return this;
    }

}

module.exports = Employee;

在EmployeePrint.js中

'use strict';

const jsonToCSV = require('json-to-csv');

class EmployeePrint {
    constructor() {
        this.name = null;
        this.payPeriod = null;
        this.grossIncome = null;
        this.incomeTax = null;
        this.netIncome = null;
        this.mySuper = null;
    }

    printPromise(data, fileName) {
        return new Promise((res, rej) => {
            jsonToCSV(data, fileName)
                .then(() => {
                    // success
                    console.log('Good, print to ' + fileName);
                    res(true);
                })
                .catch(error => {
                    // handle error
                    console.log('Print error');
                    rej(true);
                });
        });
    }

    fillData(item, taxObj) {
        let fullName = item.getFullName();
        let timePeriod = item.getTimePeriod();
        let grossIncome = item.getGrossIncome();
        let incomeTax = item.getIncomeTax(taxObj);
        let netIncome = item.getNetIncome();
        let mySuper = item.getSuper();

        this.name = fullName;
        this.payPeriod = timePeriod;
        this.grossIncome = grossIncome;
        this.incomeTax = incomeTax;
        this.netIncome = netIncome;
        this.mySuper = mySuper;

        return this; 
    }

    async print(arr, fileName, taxObj) {
        let buf = [];

        arr.forEach((item) => {
            let ep = new EmployeePrint();
            ep = ep.fillData(item, taxObj).bind(this);
            buf.push(ep);
        }).bind(this);

        return await this.printPromise(buf, fileName);
    }

}

module.exports = EmployeePrint; 

ep = ep.fillData(item, taxObj).bind(this);在forEach循环的第二次迭代中，taxObj似乎未定义。是因为循环中存在异步性质吗？如果是这样，我该如何解决？

完整代码：https://github.com/kenpeter/mb_new/tree/master/lib