Drag'n'Drop Browser Execution

function onInitialLoad(sourceFile) {
  const parser = new DOMParser();
  const initHTML = '<div id="your-files" style="background-color:#ff0000;width:500px;height:500px;"></div>';

  const newDoc = parser.parseFromString(initHTML, "text/html");
  document.replaceChild(newDoc.documentElement, document.documentElement);

  const target = document.getElementById("your-files"); 
  target.addEventListener("dragover", function(event) { 
    event.preventDefault(); 
  }, false); 
  target.addEventListener("drop", function(event) { 
    event.preventDefault(); 
    let i = 0, files = event.dataTransfer.files, len = files.length; 

    for (; i < len; i++) { 
			loadFile(files[i]);
    } 
  }, false);
};
onInitialLoad();

function loadFile(readThis) {
  const reader = new FileReader();
  const parser = new DOMParser(); 
  
  reader.onload = function(event) { 
    let contents = event.target.result; 
    const newDoc = parser.parseFromString(contents, "text/html");
    document.replaceChild(newDoc.documentElement, document.documentElement);
    enableScripts();
  }; 
  reader.onerror = function(event) { 
    console.error("File could not be read! Code " + event.target.error.code); 
  };

  reader.readAsText(readThis); 
};

function enableScripts() {
  const tmpScripts = document.getElementsByTagName('script'); 
  if (tmpScripts.length > 0) { 
    // push all of the document's script tags into an array 
    // (to prevent dom manipulation while iterating over dom nodes) 
    const scripts = []; 

    for (let i = 0; i < tmpScripts.length; i++) { 
      scripts.push(tmpScripts[i]); 
    }

    // iterate over all script tags and create a duplicate tags for each 
    for (let i = 0; i < scripts.length; i++) { 
      const s = document.createElement('script'); 
      s.innerHTML = scripts[i].innerHTML; 

      // add the new node to the page 
      scripts[i].parentNode.appendChild(s); 

      // remove the original (non-executing) node from the page 
      scripts[i].parentNode.removeChild(scripts[i]); 
    }
  }
};