pdfmake page number and local variable access from inside footer function

Having a problem figuring out a specific issue when generating a report using PDFMake. My project uses Angular 8 for context so this is inside a modal component. Code Below of a simple version I'm using for testing. How do I define this.orderNum while inside "footer: function (currentPage, pageCount)"?

@Component({
selector: 'app-utilities-print-OrderPrintModal',
templateUrl: './printtemplate.html'
})

export class OrderPrintModal implements OnInit {
@Input() passedOrderNum: string;
public orderNum: string;
public pdf: any;

ngOnInit() {
this.orderNum= this.passedOrderNum;
this.print();
}

print() {
var dd = {
pageOrientation: "portrait",
pageMargins: [20, 10, 20, 40],
pageSize: "LETTER",

footer: function (currentPage, pageCount) {
var t = {
layout: "noBorders",
fontSize: 8,
margin: [25, 0, 25, 0],
table: {
widths: ["*", "*"],
body: [
[
{ text: "Page " + currentPage.toString() + " of " + pageCount },
{ text: "orderNum " + this.orderNum }
]
]
}
};

return t;
}
this.createPDF(dd)
}

createPDF(dd: any) {
this.pdf = pdfMake.createPdf(dd);
this.pdf.getDataUrl((dataUrl) => {
const targetElement = document.querySelector('#iframeContainer');
const iframe = document.createElement('iframe');
iframe.src = dataUrl;
iframe.setAttribute("style", "width:100%; height:100%;");
targetElement.appendChild(iframe);
});
}
}


Console error is : core.js:6014 ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'orderNum' of undefined TypeError: Cannot read property 'orderNum' of undefined

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