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Create a JavaScript object for tunes, songs. The have titles, composers, and year as properties as well as an array of performers.

The Tune object must be used in an HTML5 page allowing the user to enter tunes data through a form. The entered Tune objects must be stored in an array. The page has a div element, where the array of tunes is displayed. Whenever the array is changed, the display must automatically be updated.

Optional extra: Consider introducing a possibility for deleting tunes from the tunes array.

Write a Planet class. Use it to create ten planets storing planetary information. You may find the info on: http://www.opencourse.info/astronomy/introduction/05.motion_planets/#sidereal%20period and http://www.opencourse.info/astronomy/introduction/05.motion_planets/#aphelion . You don't need more than the sample output suggests. Treat the Sun as the first planet, with all values set to zero. Write a web information page with a form that allows the user to choose a planet via a radio button. Create a change event with a handler that writes the planet's information on the screen.

Sample output for Jupiter:

Distance = 5.2028 AU
Sidereal Period = 11.862 years
Synodic Period = 398.9 days
Eccentricity = 0.048
Orbital Inclination = 1.31°

Write an HTML5 page with a form for entering credit card information. On submitting the form the content must be validated. For this purpose you must create a credit card object holding the following:

Correct information should be sent to http://x15.dk/hitme.php. Incorrect should not be submitted but return an appropriate error message asking the user for correction.

You may refer to https://www.codeproject.com/tips/253704/test-credit-card-account-numbers for numbers suitable for testing.

'use strict';
class CreditCard {
    constructor(ccno, expdate, name, cvv) {
        this.ccnumber = ccno;
        //...
    }

    isValid() {
        // code for checking
        // return false if invalid
        // else return true
        return true;
    }
}

const validate = function(e) {
    let ccnumber = document.getElementById('ccno');
    let expdate = document.getElementById('exp').value;
    // more values from form
    let cc = new CreditCard(ccnumber.value, expdate, 'Niels', '666');
    if (!cc.isValid()) {
        ccnumber.focus();
        e.preventDefault();
        return false;
    } /* if (! other tests)

    } */ else {
        return true;
    }
}

const init = function() {
    document.getElementById('formid').addEventListener('submit', validate);
}

window.addEventListener('load', init);

In the beginning were the natural numbers, ℕ, they are the numbers used for counting. Later we got what is today know as the integers, ℤ, by adding zero, 0, and the negative numbers. Later again we got the fractions, in mathematical speak the rational numbers ℚ, and all was good.

The rational numbers are the integers plus the fractions. Fractions are represented as the ratio between two integers. As an example, 3/7 is a rational number. The 3 is called the numerator. The 7 is called the denominator. Integers are fractions with a denominator of 1.

In this assignment you are going to create an object for rational numbers, and several methods for doing calculations with them. You see, some of us love the rational numbers because they are beautiful and exact. The real numbers ℝ, the numbers with decimals, are approximations.