JSFiddle - React, Tailwind, and code Playground

by lollero

HTML

<div id="block1"></div>
<div id="block2"></div>

CSS

div { background: #333; height: 30px;  }

#block1 { width: 500px; }

#block2 { 
    background: red; 
    width: 100px; 
    position: absolute;
    top: 0px;        
    right: 0px;
}

#block2.temp {
    right: auto;
    left: 0px;
}

JavaScript

$(window).resize(function() {
    
    var minus = 100;
        windowW = $(window).width(),
        block1W = $('#block1').width() + minus,
        block2 = $('#block2');
    
    if ( windowW <= block1W ) {
        block2.addClass( 'temp' );
    }
    else {
        block2.removeClass( 'temp' );
    }
    
}).resize();