params-ref.js

function example(a, b) {}

example.length === 2; // returns => true

example(1, 2, 3);
// a === 1
// b === 2
// arguments[0] === 1
// arguments[1] === 2
// arguments[2] === 3

this-ref.js

function outer() {
  var that = this;
  var inner1 = function inner1() {}; // this !== that
  var inner2 = inner1.bind(that);    // this === that
}

var-memory-ref.js

var str, str2;
var num, num2;
var bool, bool2;
var obj, obj2;
var func, func2;

str  = 'string';
num  = 5;
bool = true;
obj  = {};
func = function(){};

// str  => new primitive
// num  => new primitive
// bool => new primitive
// obj  => same object reference
// func => same object reference

str2  = str;  // new place in memory
num2  = num;  // new place in memory
bool2 = bool; // new place in memory
obj2  = obj;  // same place in memory
func2 = func; // same place in memory

is.empty(obj);   // return => true
is.empty(obj2);  // return => true
is.empty(func);  // return => true
is.empty(func2); // return => true

obj2.prop = true;
func.prop = null;

is.empty(obj);   // return => false
is.empty(obj2);  // return => false
is.empty(func);  // return => false
is.empty(func2); // return => false