An less functional solution to JS tasker, with namespacing and object constructors. Could use some bits of refactoring. Big thanks to one Franklin Webber for being awesome.

JSTaskerSolution.js

// jQuery "on page load"
$(function(){
  // Focus on the main field
  $('input#task_text').focus();

  // Object constructor for task list
  var TaskList = function(element) {
    // Assigning 'this.element' property from input (a selector). 'this.element' could be called anything.
    this.element = $(element);

    // $.proxy takes is a way to assign 'this' in a specific context (here, a function)
    this.element.on('click', $.proxy(function(event) {
      $(event.target).toggleClass('completed');
      this.updateList();
    }, this));
  };
 
  // Functional properties of each list
  TaskList.prototype = {
    tasks : function() {
      return this.element.children();
    },
    incompleteTasks: function() {
      return this.tasks().not('li.completed');
    },
    count : function() {
      return this.incompleteTasks().size();
    },
    addListItem: function(text) {
      var task_li = "<li>" + text + "</li>";
      this.element.append(task_li);
      $('input#task_text').val("");
      this.updateList();
    },
    updateList : function() {
      this.updateCounter();
      this.sortTasks();
    },
    updateCounter : function() {
      $('span#task_counter').text(this.count())
    },
    sortTasks : function() {
      var incompleted = this.incompleteTasks().detach();
      this.element.prepend(incompleted)
    }
  };

  // Assigning a TaskList, which takes the input of a selector
  var taskList = new TaskList("#tasks ul");


  // Adds list item using object; prevents page scroll
  $('form#add_task').on('submit', function(event){
    event.preventDefault();
    taskList.addListItem($('input#task_text').val());
  });
});