1  var badBrowser = false;
 2  
 3  try {
 4    // Local storage
 5    window.localStorage.setItem('test', 'test');
 6    window.localStorage.removeItem('test');
 7  
 8    // Flexbox
 9    var elTest = document.createElement('div');
10    elTest.style.display = 'flex';
11    if (elTest.style.display !== 'flex') {
12      badBrowser = true;
13    }
14  
15    // const and let check from badBrowserCheckA.js
16    if (window.localStorage.goodBrowser !== 'true') {
17      badBrowser = true;
18    }
19    window.localStorage.removeItem('goodBrowser');
20      
21  } catch (err) {
22    badBrowser = true;
23  }
24  
25  if (badBrowser) {
26    var el = document.getElementsByClassName('BadBrowser')[0];
27    el.className += ' is-open';
28    // Dumb check for known mobile OS's. Not important to catch all, just
29    // displays more appropriate information.
30    if (/iPhone|iPad|iPod|Android/i.test(navigator.userAgent)) {
31      el.className += ' is-mobile';
32    }
33  }