JSFiddle - React, Tailwind, and code Playground

HTML

<input type="file" name="file" id="file"  />

<input type="button" onClick="validate()" value="Submit">

JavaScript

function validate()
{
  var file = $('#file').val(); 

  if (file == "") {  
    alert("select file"); //alert when no file is selected
    return false;          
  }
  else
  { 
     /* get file size in MB */  
     var file_size = $('#file')[0].files[0].size / 1024 / 1024; 

     //check if file size is greater than 2MB
     if(file_size > 2) {  
       alert("File size is greater than 2MB"); return false; 
     }
     else
     {
       //submit form
     }
  } 

}