clean user state-handling & triggers based on changes

Usage:

<script type='text/javascript' src='usertrigger.min.js'></script>

Getting started

var user = new user()       // works with jquery out of the box, see jquery-agnostic example below
user.has("PhD", "input[name=PhD_date_selector]",   'change keyup' )
user.has("PhD")             // returns false

Now after entering a date in the input, it will return true:

user.has("PhD") // returns true

But we could also manually tag/untag it:

user.set("PhD", true)

NOTE #1: a state represents a combination of tags, therefore use the custom queries (see example below) for states.

Reference

user.has( tag, domselector_or_array_with_domselectors, string_with_events )    <-- query tag or initialize
               --------------------  ------------------      <-- optional

user.set( tag, true|false  )                                 <-- tag user

user.on( tag_or_function, function )                         <-- tag eventhandler

Example: tag user (multiple)

user.has("lotsofpeople", [
  "input[type=checkbox]#filter_bedrooms_4", 
  "input[type=checkbox]#filter_bedrooms_5" 
], 'change' )

Example: trigger

user.on( "lotsofpeople", 
  user.once( // you can leave this wrapper out if you want to run it more than once 
    function(user){
      setTimeout( function(){ 
        alert("It seems you are booking for a group of people.<br>Feel free to chat with our supportdesk to find out a good deal")
      }, 10000 )
    }
  )
)

Example: custom query & custom trigger

user.knowsDates = function(){ 
  return user.has("PhD") && user.has("bachelordegree") 
}

user.on( user.knowsDates, 
  user.once( // you can leave this wrapper out if you want to run it more than once 
    function(user){
      alert("It seems you know exactly when you want to stay in <city>, did you know there's <event> during that time?")
    }
  )
)

Without jquery

The solution above works out of the box with jQuery, however for vanilla javascript you make a simple jquery stub:

// not tested below (please do a PR)

var myselector = function(selector){
  var element, elements, l, len, results;
  if (selector[0] === "#") {
    element = document.querySelector(selector);
    if (element) result = element
  } else {
    result = elements
  }
  return {
    data: result,
    on: function(event,cb){
      // 
    }
  }
}

var user = new user({'$':myselector})

NOTE: the selector engine only needs to support cssselectors and jQuery's on( event(s) , cb ) function