Script fails to submit to hubspot contacts with form API

[Kristaf]

Am trying to submit sample data to hubspot contacts using custom form fields and hubspot form API but it's failing. Need some help where am going wrong. This is my javascript:

function formv3(){
    let xhr = new XMLHttpRequest();
    let url = 'https://api.hsforms.com/submissions/v3/integration/submit/62515/b68a1eb2-9c96-4483-baec-815482d30083';

    // Example request JSON:
    let data = {
        "fields": [
            {
                "name": "email",
                "value": "example@example.com"
            },
            {
                "name": "firstname",
                "value": "Jeff"
            }
        ]
    };

    let final_data = JSON.stringify(data);

    xhr.open('POST', url);
    // Sets the value of the 'Content-Type' HTTP request headers to 'application/json'
    xhr.setRequestHeader('Content-Type', 'application/json');

    xhr.onreadystatechange = function() {
        if(xhr.readyState == 4 && xhr.status == 200) {
            alert(xhr.responseText); // Returns a 200 response if the submission is successful.
        } else if (xhr.readyState == 4 && xhr.status == 400){
            alert(xhr.responseText); // Returns a 400 error if the submission is rejected.
        } else if (xhr.readyState == 4 && xhr.status == 403){
            alert(xhr.responseText); // Returns a 403 error if the portal isn't allowed to post submissions.
        } else if (xhr.readyState == 4 && xhr.status == 404){
            alert(xhr.responseText); //Returns a 404 error if the formGuid isn't found
        }
    };
    xhr.send(final_data)
}

formv3();

[Kristaf]

I have found out why it wasn't, the portal id was wrong and I added the correct one. Now it works. Thanks