safe_approach.js

Browser.prototype.isGradeA = function() {
  var browser = this
  browser.on("response", function(res, target) {
    var window = browser.window
    var document = browser.document
    var onMobileInitMakeGradeA = function() {
      if (window.$) {
        window.$(document).on("mobileinit", function() {
          window.$.mobile.gradeA = function() { return true }
        })
      } else {
        process.nextTick(onMobileInitMakeGradeA)
      }
    }
    if (res.url.match(/mobile/)) {
      onMobileInitMakeGradeA()
    }
  })
}

unsafe_approach.js

Browser.prototype.isGradeA = function() {
  var browser = this
  browser.on("response", function(res, target) {
    var window = browser.window
    var document = browser.document
    if (res.url.match(/mobile/)) {
      window.$(document).on("mobileinit", function() {
        window.$.mobile.gradeA = function() {
          return true
        }
      })
    }
  })
}