function HTMLEncode(html) {
 var temp = document.createElement("div");
 (temp.textContent != null) ? (temp.textContent = html) : (temp.innerText = html);
 var output = temp.innerHTML;
 temp = null;
 return output;
}
var tagText = "<p><b>123&456</b></p>";
console.log(HTMLEncode(tagText));//<p><b>123&456</b></p> 

function HTMLDecode(text) { 
 var temp = document.createElement("div"); 
 temp.innerHTML = text; 
 var output = temp.innerText || temp.textContent; 
 temp = null; 
 return output; 
} 
var tagText = "<p><b>123&456</b></p>";
var encodeText = HTMLEncode(tagText);
console.log(encodeText);//<p><b>123&456</b></p>
console.log(HTMLDecode(encodeText)); //<p><b>123&456</b></p>