TypeError: Cannot read properties of undefined (reading 'null')

Ask the Experts and Postman Tips
1

I have body response:

“persons”: [
{
“id”: 377,
“forename”: “Forename 493068”,
“surname”: “Surname 493068”,
“dateOfBirth”: “1971-06-16”
},
{
“id”: 376,
“forename”: “Forename 493067”,
“surname”: “Surname 493067”,
“dateOfBirth”: “1971-01-14”
},

Here’s an outline with best practices for making your inquiry.

I check if dateOfBirth is null or string:

const jsonData = pm.response.json();
pm.test(“Test work with loops persons”, () => {
console.log(jsonData.persons.length);
pm.expect(jsonData.persons).to.be.an(‘array’).that.is.not.empty;
for(let i = 0; i < jsonData.value.persons.length; i++)
var expiryDate = jsonData.accounts[i].dateOfBirth;
pm.expect(dateOfBirth).to.be.oneOf([null,“string”]);
I
My question:

TypeError: Cannot read properties of undefined (reading ‘null’)
How to fix this check?

2

Hi @cryosat-observer-223

I think you are using the wrong variable name.

var expiryDate = jsonData.accounts[i].dateOfBirth;
pm.expect(dateOfBirth).to.be.oneOf([null,“string”]);

Try changing it to;

var expiryDate = jsonData.accounts[i].dateOfBirth;
pm.expect(expiryDate).to.be.oneOf([null,“string”]);
3

yep, I detected wrong var name later, thanks
But now I see the next error:
AssertionError: expected ‘1971-06-16’ to be one of [ null, ‘string’ ]

4

Please consider the following…

jsonData = 
    [{
    "id": 377,
    "forename": "Forename 493068",
    "surname": "Surname 493068",
    "dateOfBirth": "1971-06-16"
    },
    {
    "id": 376,
    "forename": "Forename 493067",
    "surname": "Surname 493067",
    "dateOfBirth": "1971-01-14"
    },
    {
    "id": 375,
    "forename": "Forename 123456",
    "surname": "Surname 123456",
    "dateOfBirth": null
    }];

console.log(jsonData.length);

pm.test("Array check", () => {
    pm.expect(jsonData).to.be.an("array").that.is.not.empty;
});

for (let i = 0; i < jsonData.length; i++) {

    var expiryDate = jsonData[i].dateOfBirth;
    console.log(expiryDate);

    pm.test("String?", () => {
        pm.expect(expiryDate).to.be.an("string");
    });

    // oneOf checks values not types, so this will fail.
    pm.test("Expiry date", () => {
        pm.expect(expiryDate).to.be.oneOf([null,"string"]);
    });

    // This will work as long as its a string
    pm.test("Expiry date v2", () => {
        pm.expect(typeof(expiryDate)).to.be.oneOf(["string", null]);
        // null returns the type as an object
    });

};
5

You probably need a function to help with this.

jsonData = 
    [{
    "id": 377,
    "forename": "Forename 493068",
    "surname": "Surname 493068",
    "dateOfBirth": "1971-06-16"
    },
    {
    "id": 376,
    "forename": "Forename 493067",
    "surname": "Surname 493067",
    "dateOfBirth": "1971-01-14"
    },
    {
    "id": 375,
    "forename": "Forename 123456",
    "surname": "Surname 123456",
    "dateOfBirth": null
    }];

console.log(jsonData.length);

// helper function to deal with null
function getType(value) {
    if (value === null || value === undefined) return null
  
    const type = typeof(value)
  
    if (type == 'object') {
        if (value instanceof Array) return 'array'
        if (value instanceof Date) return 'date'
    }

    return type
};

pm.test("Array check", () => {
    pm.expect(jsonData).to.be.an("array").that.is.not.empty;
});

for (let i = 0; i < jsonData.length; i++) {

    var expiryDate = jsonData[i].dateOfBirth;
    console.log(expiryDate);

    // Using the helper function
    pm.test("Expiry date v3", () => {
        pm.expect(getType(expiryDate)).to.be.oneOf(["string", null]);
    });

};
6

As this is an array, you can also use a forEach loop.

jsonData = 
    [{
    "id": 377,
    "forename": "Forename 493068",
    "surname": "Surname 493068",
    "dateOfBirth": "1971-06-16"
    },
    {
    "id": 376,
    "forename": "Forename 493067",
    "surname": "Surname 493067",
    "dateOfBirth": "1971-01-14"
    },
    {
    "id": 375,
    "forename": "Forename 123456",
    "surname": "Surname 123456",
    "dateOfBirth": null
    }];

console.log(jsonData.length);

// helper function to deal with null
function getType(value) {
    if (value === null || value === undefined) return null
  
    const type = typeof(value)
  
    if (type == 'object') {
        if (value instanceof Array) return 'array'
        if (value instanceof Date) return 'date'
    }

    return type
};

pm.test("Array check", () => {
    pm.expect(jsonData).to.be.an("array").that.is.not.empty;
});

jsonData.forEach(element => {

    var expiryDate = element.dateOfBirth;
    console.log(expiryDate);
 
   // Using the helper function
    pm.test("Expiry date v3", () => {
        pm.expect(getType(expiryDate)).to.be.oneOf(["string", null]);
    });
    
});
8

This helped, Thanks - typeof - the solution for my case