JSFiddle - React, Tailwind, and code Playground

HTML

<div id="background"></div>
<div id="content"></div>

CSS

#background {
    /* fixed position - aways on top of the screen */
    position: fixed;
    top: 0;
    left: 0;
    
    /* set repeat-x so it doesn't run off */
    background: url(http://dummyimage.com/3000x100/333/999.png&text=foobarfoobarfoobarfoobarfoobar) repeat-x;
    
    /* you MUST set width and height or it won't display */
    width: 100%;
    height: 100px;
    
    /* -1 to ensure it will always be in background */
    z-index: -1;
}

#content{
    width: 500px;
    margin: 0 auto;
    background: #b0b0b0;
}

JavaScript

// add some content
for(var i=0;i<50;i++)
    $("#content").append('<p>some text</p>');

// event which fires on scroll
$(window).scroll(function () {
    // parse the value of current background position and add window.scrollY - vertical scroll (divide this for slower background scroll)
    var offset = parseInt($("#background").css("background-position-x")) + window.scrollY;
    $("#background").css("background-position-x", offset + "px");
});