copy localstorage javascript

localStorage.setItem('user_name', 'Rohit'); //store a key/value
var retrievedUsername = localStorage.getItem('user_name'); //retrieve the key

localStorage.setItem("user_name", "Bob");

document.body.addEventListener("click", function(){
  alert(localStorage.getItem("user_name"))
});

var data = JSON.parse(/*previously copied stringified JSON from clipboard*/);
Object.keys(data).forEach(function (k) {
  localStorage.setItem(k, data[k]);
});