JSFiddle - React, Tailwind, and code Playground

HTML

<div id="A"></div>
<div id="B"><button>toggle</button></div>

CSS

html, body {
    margin: 0;
    padding: 0;
    border: 0;
}
#A, #B {
    position: absolute;
}
#A {
    top: 0px;
    width: 200px;
    bottom: 0px;
    background:orange;
}
#B {
    top: 0px;
    left: 200px;
    right: 0;
    bottom: 0px;
    background:green;
}
#BB {
    top: 0px;
    left: 0px;
    right: 0;
    bottom: 0px;
    background:green;
}

JavaScript

$('button').toggle(

function() {
    $('#B').animate({left: 0})
}, function() {
    $('#B').animate({left:200})
})