Element.outerHTML

var content = element.outerHTML;

element.outerHTML = htmlString;

// HTML:
// <div id="d"><p>Content</p><p>Further Elaborated</p></div>

d = document.getElementById("d");
console.log(d.outerHTML);

// '<div id="d"><p>Content</p><p>Further Elaborated</p></div>'
//    .

// HTML:
// <div id="container"><div id="d">This is a div.</div></div>

container = document.getElementById("container");
d = document.getElementById("d");
console.log(container.firstChild.nodeName); // "DIV" .

d.outerHTML = "<p>This paragraph replaced the original div.</p>";
console.log(container.firstChild.nodeName); // "P" .

// #d div    ,
//  p  .

var div = document.createElement("div");
div.outerHTML = '<div class="test">test</div>';
//   DOMException  .
console.log(div.outerHTML); // : "<div></div>"

var p = document.getElementsByTagName("p")[0];
console.log(p.nodeName); // "P" .
p.outerHTML = "<div>This div replaced a paragraph.</div>";
console.log(p.nodeName); //  "P" .