JSFiddle - React, Tailwind, and code Playground

HTML

<form  class="upload-form">
        <input class="upload-file" data-max-size="2048" type="file" >
        <input type=submit>
    </form>

JavaScript

$(function(){
    var fileInput = $('.upload-file');
    var maxSize = fileInput.data('max-size');
    $('.upload-form').submit(function(e){
        if(fileInput.get(0).files.length){
            var fileSize = fileInput.get(0).files[0].size; // in bytes
            if(fileSize>maxSize){
                alert('file size is more then' + maxSize + ' bytes');
                return false;
            }else{
                alert('file size is correct- '+fileSize+' bytes');
            }
        }else{
            alert('choose file, please');
            return false;
        }
        
    });
});