How to set "N/A" if data is null in angular

Lets say i have a table and sometimes few data’s can be null but null data are showing undefined at the table instead of showing undefine i want to show "N/A" how can i achieve that ill share an image and a code below.

at the above image under reference data some of the data showing undefine because it is null i want it to show "N/A". I’ll share the code below. Below code there is "a.normalRange" variable that variable holds the reference data.

 var col = ["Test Name", "Result", "Unit" , "Reference"];
    this.hubxDataItemSpList.forEach((a) => {
      medicineInfo = this.hubxDataItemSpList.find(x => x.id == a.id);
      rows.push(['' + a.categoryName +' '+ a.itemTitle + '', '' + a.itemValue + '', '' + a.itemUnit ,'' + a.normalRange]);
    });

this is my Model

export class HubxDataItemSpModel {
    id: number;
    categoryId: number;
    categoryName:string;
    itemTitle: string;
    itemUnit: string;
    isActive: boolean=true;
    itemValue: string;
    patientId: number;
    clinicianHubXSign : string;
    isAprrovedStatus : boolean;
    isTestApproved : boolean;
    phySignDate : Date;
    notes : string;
    normalRange : string;
    //base64:any;
    isDeleted: boolean;
    createdDate : Date
}

And this is how i define my model at my component class

hubxDataItemSpList : Array<HubxDataItemSpModel>=[];

And this is how i print the table

 doc.autoTable({
            columnStyles: {
              0: { cellWidth: 45 },
              1: { cellWidth: 45 },
              2: { cellWidth: 45 },
              3: { cellWidth: 45 }
            },
            head: [col],
            body: rows,
            startY: 100,
            theme: 'plain',
            tableLineColor: [242, 238, 238],
            tableLineWidth: 0.5,
            styles: {
              font: 'courier',
              lineColor: [242, 238, 238],
              lineWidth: 0.5
            },
          });

Data from APi

{
  "expires_in": 0,
  "data": [
    {
      "id": 1727,
      "categoryId": 2,
      "categoryName": "Lipid Profile",
      "itemTitle": "Total Cholesterol",
      "itemUnit": "mg/dl",
      "patientId": 3224,
      "itemValue": "3.2",
      "isTestDone": true,
      "clinicianHubXSign": "0",
      "isAprrovedStatus": false,
      "isTestApproved": false,
      "normalRange": "3.6-6.5",
      "isActive": true,
      "createdDate": "2022-07-20T13:17:42.9735718",
      "isDeleted": false,
      "createdBy": 1,
      "phySignDate": "0001-01-01T00:00:00"
    },
    {
      "id": 1728,
      "categoryId": 2,
      "categoryName": "Lipid Profile",...

>Solution :

If any other value need to be checked call isValueEmpty method with that value.

const col = ["Test Name", "Result", "Unit" , "Reference"];
this.hubxDataItemSpList.forEach((a) => {
    medicineInfo = this.hubxDataItemSpList.find(x => x.id == a.id);
    const normalRange = changeIfValueEmpty(a.normalRange);
    rows.push(['' + a.categoryName +' '+ a.itemTitle + '', '' + a.itemValue + '', '' + a.itemUnit ,'' + normalRange]);
});

function changeIfValueEmpty(value) {
    value = value ?? ''; // reassigned if value is null or undefined
    return (value value.trim() === '') ? 'N/A' : value; // to check value only contains whitespace
}