How do I retrieve values from checkboxes in JavaScipt, using onchange to trigger a function?

I'm a High School student who takes a programming course (JavaScript) at school. We just had a test (which I miserably failed), but we are allowed to try again.

I have a couple of checkboxes. They all have an onchange which triggers a function later. I want to retrieve their values when I click on the checkboxes.

I've browsed around here a bit and seen something called jQuery. I have no idea what that is, so I would highly appreciate to get my help in pure JavaScript.

Okay, here is what I have of code. Note: Some variables and such are in Norwegian. I don't think it should be a problem, since I show the references to all.

My inputs (checkboxes):

<input type="checkbox" class="tur" value="0" onchange="funcSjekkBoks(this)">
<input type="checkbox" class="tur" value="1" onchange="funcSjekkBoks(this)">
<input type="checkbox" class="tur" value="2" onchange="funcSjekkBoks(this)">
<input type="checkbox" class="tur" value="3" onchange="funcSjekkBoks(this)">
<input type="checkbox" class="tur" value="4" onchange="funcSjekkBoks(this)">

I only need their value to be numbers, since I will use those in reference to an array list I have later.

Here is my function:

var inputTur = document.getElementsByClassName("tur");
console.log(inputTur);

        function funcSjekkBoks(checkboxEl) {
            var resultatListe = [];
            if (checkboxEl.checked) {
                resultatListe.push(inputTur.value);
                console.log(resultatListe);
            }
            else {
                console.log("usant")
            }
        }

What I would like to happen (if all checkboxes are checked from top to bottom):

resultatListe = [0, 1, 2, 3, 4]
When I uncheck a checkbox, it's value will be removed from the array.

Here is what currently happens:
When I check a checkbox I get [undefined] in my console, when I uncheck a checkbox i get usant (although that is the expected response, I haven't worked with the else part of my if-sentence yet.)

I am very thankful for all responses. This is my first time using stack overflow.