Single responsibility principle (Decoupled code)

After Decoupling

function AjaxForm($el) {
	this.$form = $el;
	this.form = $el[0]; // Internal state via properties
	this.$form.on('submit', $.proxy(this.submit, this));
};

AjaxForm.prototype = {
	submit: function(e) { // Named Functions
		e.PreventDefault();
		var this = this;
		
		$.ajax({ // Single responsibility principle
			url: _this.form.action,
			type: _this.form.method,
			success: $proxy(this.onSuccess, _this)
		});
	},

	onSuccess: function(data) {
		$({}).trigger('save success', data); // Loose coupling
		this.reset();
	},
	reset: function() {
		this.form.reset();
	}
};

Before Decoupling

$('form#tweet').on('submit', function(e) { // Anon function
  e.preventDefault();
  
  var _this = this,
    $tweets = $('#tweets'), // Tight coupling
    $this = $(this),
    $textarea = $this.find('textarea'),
    tweet = $textarea.val();
    
  $.ajax({
    url: $this.attr('action'),
    type: $this.attr('method'),
    success: function() { // Nested Callback
      $twets.append('li' + tweet + '</li'); // HTML templating
      _this.reset();
    }
  })
})