JSFiddle - React, Tailwind, and code Playground

HTML

<div>Hello world!</div>

CSS

div{
    height: 50px !important;
    width:50px;
    background-color:red !important;
    color:green !important;
}

JavaScript

$.fn.extend({
    cssi:function(obj){
        var $target=this;
        $.each(obj,function(i,e){
            var initialVal=$target.css(i);
            $target.css(i,e);
            if($target.css(i)==initialVal){ //add !important only if the value didn't change
                if(!isNaN(e)) e+="px";
                e+=" !important";
                $target.css(i,""); // clear any prior rules
                $target[0].style.cssText+=camelToDash(i)+":"+e;
            }         
        });
        return this;
    }
});

function camelToDash(str) {
    return str.replace(/\W+/g, '-')
    .replace(/([a-z\d])([A-Z])/g, '$1-$2')
    .toLowerCase();
}

$(function(){
    //Demo
    $("div").cssi({
        backgroundColor:"blue",
        height:100,
        width:100,
        color:"red"
    });
});