JSFiddle - React, Tailwind, and code Playground

HTML

<div id="content">                                                                                                                                  
    <div id="fixed_header">
        <a href="Javascript:" id="position">Click</a>
    </div>
    
    <p>Some content</p>    
</div>

<div id="div1"></div>

CSS

#content {
    height: 1000px;
    position: relative;
    padding-top: 100px;
}

#fixed_header {
    height: 50px;
    top: 10px;
    left: 0;
    background: red;
    position: fixed;
    width: 100%;
}

#div1 {
   height: 50px;
   left: 200px;
   top: 0;
   background: blue;
   position: fixed;
   width: 100px;    
}

JavaScript

header = $("#fixed_header");

$("#position").click(function() {
    $("#div1").position({
        my: "top",
        at: "bottom",
        of: header
    });
});