How to calculate the offset of an element inside a block on the wheel event?

Question

JavaScript

Colleagues of the good time of the day, I ask for the help of experts, because I'm stuck on one moment. there is a list:

<div class="container">
        <div class="layout">
            <div class="item">
                <div class="header">name</div>
                <ul>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                </ul>
            </div>
            <div class="item">
                <div class="header">name</div>
                <ul>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                    <li>text</li>
                </ul>
            </div>
        </div>
    </div>

when the wheel event occurs, the layout is shifted, there are no problems here:

_whell_action(e) {

        let direction = -Math.sign(e.deltaY);
        let step = 5 * direction;

        this.layout.style.top = (this.layout.offsetTop + step) + 'px';

        if (this.layout.offsetTop >= 0) this.layout.style.top = '0px';
        if (this.layout.offsetTop <= (this.container.clientHeight - this.list_height)) 
            this.layout.style.top = (this.container.clientHeight - this.list_height) + 'px';

        let header = this.current_item.querySelector('.header');
             header.style.top = (header.offsetTop + step) + 'px';

    }

But I can't calculate the distance to move the header in the same direction inside the item, as long as the header is inside. I define the current item and how to determine the offset? please help, thanks in advance