How do I clear local storage using javascript?

You can clear or delete key in localStorage using Javascript as per below example

localStorage.removeItem("KeyName"); //remove item from local storage based on key name

To Clear all keys at once

localStorage.clear();  //clear all key at once

To Retrieve value based on keys

// Retrieve the object from storage
var retrievedValue = localStorage.getItem('YourKeyName');

Read Local storage in javascript for more complete details about localStorage in Javascript.

You should use "window" to remove global storage

 window.localStorage.removeItem('KeyName');

OR

If you want to delete or clear local storage on windows load

window.onbeforeunload = function() {
  localStorage.removeItem(key);
  return '';
};

This should work.