JSFiddle - React, Tailwind, and code Playground

by John Doe

HTML

<input type="file" onchange="previewFile()"><br>
<img src="" height="200" alt="Image preview...">

JavaScript

function previewFile(){
       var preview = document.querySelector('img'); //selects the query named img
       var file    = document.querySelector('input[type=file]').files[0]; //sames as here
       var reader  = new FileReader();

       reader.onloadend = function () {
           preview.src = reader.result;
       }

       if (file) {
           reader.readAsDataURL(file); //reads the data as a URL
       } else {
           preview.src = "";
       }
  }

  previewFile();  //calls the function named previewFile()