How do I get my code to show the key in the console? [duplicate]

Question

let formDataContainer = new Array();

function appendFormData(firstNamePar, lastNamePar, messagePar) {

    function Person(firstNamePar, lastNamePar, messagePar){
        this.first_Name = firstNamePar;
        this.last_Name = lastNamePar;
        this.my_Message = messagePar;
    }

    let person1 = new Person(firstNamePar, lastNamePar, messagePar);
    formDataContainer.push(person1);
};

submitButton.addEventListener('click', appendFormData(firstName.value, lastName.value, message.value));
console.log(formDataContainer[0]);

BUT MY OUTPUT IS:

Person {first_Name: '', last_Name: '', my_Message: ''}

AND NOT:

Person {first_Name: 'Raven', last_Name: 'Volt', my_Message: 'Hello world'}

Answer 1

change the code to this

let formDataContainer = new Array();

function appendFormData(firstNamePar, lastNamePar, messagePar) {

    function Person(firstNamePar, lastNamePar, messagePar){
        this.first_Name = firstNamePar;
        this.last_Name = lastNamePar;
        this.my_Message = messagePar;
    }

    let person1 = new Person(firstNamePar, lastNamePar, messagePar);
    formDataContainer.push(person1);
};

submitButton.addEventListener('click', () => appendFormData(firstName.value, lastName.value, message.value));
console.log(formDataContainer[0]);

you are calling appendFormData when you were declaring the event listener