My JavaScript code with objects and methods isn't working

Try something like this for understanding:

function Person() {
  this.name;
  this.surname;
  this.age;
  this.favourite_colour;
  this.assign = function(n, s, a, fc) {
    this.name = n;
    this.surname = s;
    this.age = a;
    this.favourite_colour = fc;
  }
}
var p = new Person(); // create object
p.assign("Plamen", "Dobrev", "18", "blue")
alert(p.name);

var p = [];
p.push(new Person());
p[0].assign("Plamen", "Dobrev", "18", "blue"); // first index
alert(p[0].age); // get age of first index for example

Plamen. Glad you're taking an interest in web development and JavaScript, hope you learn a lot.

As pointed out by a few members you mis-spelled the word `color - hit F12 on your browser to open the console and you'll get useful hints when there's an error. You can also write data directly to the console from your JavaScript code:

console.log("Hi, Plamen!");

There's some really cool things we can do in JavaScript, your code is great but we could tidy it up and make it cooler. The great thing about our object function is that we really only need to have one of them. We can use it to create multiple instances of the object, you could have a single person function, like this:

function person(name, surname, age, favourite_color) {
    this.name = name;
    this.surname = surname;
    this.age = age;
    this.favourite_color = favourite_color;
}

And use it to create lot's of people, every person you create from this object function will inherit the properties and methods of the object function.

person_1 = new person("My name", "My surname", 38, "blue");
person_2 = new person("Your name", "Your surname", 123, "magenta");
person_3 = new person("Someone", "else", 4321, "purple");

document.write("Person 1 name: " + person_1.name + " " + person_1.surname);
document.write("Person 2 name: " + person_2.name + " " + person_2.surname);
document.write("Person 3 name: " + person_3.name + " " + person_3.surname);

// Or, view output in console

console.log("Person 1 name: " + person_1.name + " " + person_1.surname);
console.log("Person 2 name: " + person_2.name + " " + person_2.surname);
console.log("Person 3 name: " + person_3.name + " " + person_3.surname);

Think of the function as a sort of template that can be used to create many instances of the object. Your instances can inherit methods as well as properties:

function person(name, surname, age, favourite_color) {
    this.name = name;
    this.surname = surname;
    this.age = age;
    this.favourite_color = favourite_color;

    this.changeFavouriteColor = function(color) {
        this.favourite_color = color;
    };

    this.changeAge = function(age) {
        this.age = age;
    };
};

person_1 = new person("me", "misturr", 20, "orange");
person_2 = new person("him", "surrr", 50, "yellow");

person_1.changeAge(21);
person_2.changeFavouriteColor("green");

console.log(`${person_1.name} is ${person_1.age} years old`);
console.log(`${person_2.name}'s favourite color is ${person_2.favourite_color}`);

JavaScript is pretty cool, hope you have fun and learn more.