JSFiddle - React, Tailwind, and code Playground

HTML

<div id="main" class="main">
    
</div>
<footer></footer>

CSS

#main{
    background-color:red;
    width:100%;
    min-height:100px;
}
footer{
    background-color:blue;
    height:70px;
    width:100%;
}

JavaScript

$(window).resize(function(){
    calc();
});

function calc(){
    var height = $(window).height() - 70;
    $('#main').css("height", height);
}

calc();