checkbox localstorage if checkbox checked do function

how add localstorage on checkbox, is checked do this x function else do nothing!

my checkbox

<input type="checkbox" name="onoffswitch" class="flipswitch" checked>

this is the function what I want to do if checkbox is checked

document.body.onclick=function(e){
  e.preventDefault();
  return false;
}
window.onload=function() {
  document.body.onclick=null;
  var links = document.querySelectorAll(".search-results a");
  for (var i=0;i<links.length;i++) {
    links[i].target="_blank";
  }
}