webfonts + localstorage

loadFonts.js

function loadFonts(url, defer){
  
  localStorage.fontUrl == url
    ? inject(localStorage.font)
    : defer
      ? window.addEventListener('DOMContentLoaded', load)
      : load()
 
  function load(){
    var req = new XMLHttpRequest()
    req.open('GET', url, true)
    req.onload = function(){
      inject(req.responseText)
      localStorage.font = req.responseText
      localStorage.fontUrl = url
    }
    req.send()
  }
 
  function inject(css){
    var style = document.createElement('style')
    style.textContent = css
    document.head.appendChild(style)
  }
 
}