JSFiddle - React, Tailwind, and code Playground

HTML

Seleziona un'immagine: 
<input type="file" onchange="previewImage(this)" />
<div>
<img src="" id="preview" />
</div>

JavaScript

function previewImage(input) {
  var preview = document.getElementById('preview');
  var file    = input.files[0];
  var reader  = new FileReader();
  
  reader.addEventListener("load", function () {
    preview.src = reader.result;
  }, false);

  if (file) {
    reader.readAsDataURL(file);
  }
}