JSFiddle - React, Tailwind, and code Playground

by netnguyen270

HTML

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>
  <div class="vb-content">
    <h1>Check File Size</h1>
    <input type="file" id="file-uploader">
    <div id="feedback"></div>
  </div>
</body>
</html>

CSS

html {
  min-height: 100vh;
}

body {
  background: #000000;
  color: #FFFFFF;
}

.vb-content {
  display: flex;
  justify-content: center;
  flex-direction: column;
  align-items: center;
  font-family: 'Roboto Mono', monospace;
}

JavaScript

const fileUploader = document.getElementById('file-uploader');
const feedback = document.getElementById('feedback');

fileUploader.addEventListener('change', (event) => {
  const file = event.target.files[0];
  console.log('file', file);
  
  const size = file.size;
  console.log('size', size);
  let msg = '';
  
  if (size > 1024 * 1024) {
    msg = `<span style="color:red;">The allowed file size is 1MB. The file you are trying to upload is of ${returnFileSize(size)}</span>`;
  } else {
    msg = `<span style="color:green;"> A ${returnFileSize(size)} file has been uploaded successfully. </span>`;
  }
  feedback.innerHTML = msg;
});

function returnFileSize(number) {
  if(number < 1024) {
    return number + 'bytes';
  } else if(number >= 1024 && number < 1048576) {
    return (number/1024).toFixed(2) + 'KB';
  } else if(number >= 1048576) {
    return (number/1048576).toFixed(2) + 'MB';
  }
}