Polish

google-music-account-switcher.html

<input type="text" placeholder="Your Google Music account" size="30"
       id="gmusic-switcher-account"
       onkeyup="
  (function() {
    var account = document.getElementById('gmusic-switcher-account').value;
    var bookmarklet = document.getElementById('gmusic-switcher-bookmarklet');
    var hrefTemplate = bookmarklet.getAttribute('data-href');

    var email;
    if (validEmail(account)) {
      email = account;
      bookmarklet.style.display = 'block';
      bookmarklet.textContent = 'Switch Google Music using ' + account;
      bookmarklet.href = hrefTemplate.replace('YOUR_EMAIL', email);
    } else {
      email = '';
      bookmarklet.style.display = 'none';
      bookmarklet.href = null;
    }

    function validEmail(s) {
      return /[a-z0-9._]+@[a-z0-9._]+\.[a-z]+/.test(s.toLowerCase());
    }
  })()
"/>
<a data-href="javascript:
  (function() { /* IIFE to avoid polluting window */
    /* Configuration: the Google Account you subscribed to Google Music with,
       will be substituted by the wrapper page */
    var email = 'YOUR_EMAIL';
    /* Helpers */
    var forEach = Array.prototype.forEach.call;
    var filter = Array.prototype.filter.call;
    /* Dismiss modal window */
    var modals = document.querySelectorAll('.signup-flow, .signup-flow-bg');
    forEach(modals, function(n){ n.remove(); });
    var switcher = document.getElementById('gbgs4dn');
    if (switcher) {
      switcher.click();
      /* Find account switcher entry for the correct account */
      var accounts = document.querySelectorAll('.gbps3');
      var musicAccount = filter(accounts, function(n){ return n.textContent == email; })[0];
      /* and activate it if found */
      if (musicAccount) {
        musicAccount.click();
      } else {
        alert('Cannot switch to ' + email + '; are you sure you are logged in?');
      }
    } else {
      alert('Cannot find the account switcher. Are you in the right place?');
    }
  })()
" id="gmusic-switcher-bookmarklet" style="display: none">Please enter the email of your Google Music account</a>