create a div using javascript code example

Example 1: add element to body javascript

var elem = document.createElement('div');
elem.style.cssText = 'position:absolute;width:100%;height:100%;opacity:0.3;z-index:100;background:#000';
document.body.appendChild(elem);

Example 2: document create element

document.body.onload = addElement;

function addElement () { 
  // create a new div element 
  var newDiv = document.createElement("div"); 
  // and give it some content 
  var newContent = document.createTextNode("Hi there and greetings!"); 
  // add the text node to the newly created div
  newDiv.appendChild(newContent);  

  // add the newly created element and its content into the DOM 
  var currentDiv = document.getElementById("div1"); 
  document.body.insertBefore(newDiv, currentDiv); 
}