How I Learned to Stop Worrying and Drop the Semicolon

after.js

device = function(){
  var flags = {}, ua = navigator.userAgent, el = document.createElement('div')
  function flag(names) {
    document.body.className += (document.body.className ? ' ' : '') + names
    names = names.split(' ')
    for (var i = 0; i < names.length; i++) flags[names[i]] = true
  }
  if (ua.indexOf('MSIE ') > -1) flag('msie');
  if (ua.indexOf('Firefox') > -1) flag('firefox')
  if (ua.indexOf('(iPad') > -1) flag('ios ipad')
  if (ua.indexOf('(iPhone') > -1 || ua.indexOf('(iPod') > 1) flag('ios iphone');
  el.setAttribute('ongesturestart', 'return;')
  if (typeof el.ongesturestart === 'function') flag('touch')
  if (window.navigator.standalone) flag('standalone')
  if (window.devicePixelRatio >= 2) flag('retina')
  if(!!document.createElement('video').canPlayType) flag('video')
  return flags
}()

before.js

device = (function() {
  var flags = {}, ua = navigator.userAgent, el = document.createElement('div');
  function flag(names) {
    document.body.className += (document.body.className ? ' ' : '') + names;
    names = names.split(' ');
    for (var i = 0; i < names.length; i++) {
      flags[names[i]] = true;
    }
  }
  if (ua.indexOf('MSIE ') > -1) {
    flag('msie');
  }
  if (ua.indexOf('Firefox') > -1) {
    flag('firefox');
  }
  if (ua.indexOf('(iPad') > -1) {
    flag('ios ipad');
  }
  if (ua.indexOf('(iPhone') > -1 || ua.indexOf('(iPod') > 1) {
    flag('ios iphone');
  }
  el.setAttribute('ongesturestart', 'return;');
  if (typeof el.ongesturestart === 'function') {
    flag('touch');
  }
  if (window.navigator.standalone) {
    flag('standalone');
  }
  if (window.devicePixelRatio >= 2) {
    flag('retina');
  }
  if(!!document.createElement('video').canPlayType) {
    flag('video');
  }
  return flags;
}());

Writing this piece of code made me finally decide to drop the semicolon and start following the Zepto.js code style (see https://github.com/madrobby/zepto#readme); it’s just so much more readable.

I wouldn't say the (highly subjective) readability gain is so much caused by dropping the semicolon's as it is by embracing the loosely typed language characteristics in JavaScript (and getting rid of brackets for one line statements).

And on another note: Line 8 and 11 still has semicolon's :)

Line 11, ua.indexOf('(iPod') > 1, you meant > -1, right?

Also, if your intent in using the opening parenthesis there is to prevent catching the string iPod as part of another word, you could also opt for the \b word boundary character and instead do /\biPod\b/.test(ua) in case the UA ever switches away from parens (and I believe regex is also faster).