Real, deep copied objects.

clone.js

function clone( obj ) {
  var val, length, i,
    temp = [];

  if ( Array.isArray(obj) ) {
    for ( i = 0, length = obj.length; i < length; i++ ) {
      // Store reference to this array item's value
      val = obj[ i ];

      // If array item is an object (including arrays), derive new value by cloning
      if ( typeof val === "object" ) {
        val = clone( val );
      }
      temp[ i ] = val;
    }
    return temp;
  }

  // Create a new object whose prototype is a new, empty object,
  // Using the second properties object argument to copy the source properties
  return Object.create({}, (function( src ) {
    // Initialize a cache for non-inherited properties
    var props = {};

    Object.getOwnPropertyNames( src ).forEach(function( name ) {
      // Store short reference to property descriptor
      var descriptor = Object.getOwnPropertyDescriptor( src, name );

      // Recurse on properties whose value is an object or array
      if ( typeof src[ name ] === "object" ) {
        descriptor.value = clone( src[ name ] );
      }
      props[ name ] = descriptor;
    });
    return props;
  }( obj )));
}           

test.js

var orig = {
      foo: "bar",
      inner: {
        prop: false,
        array: [ 1, 2, 3, 4, 5 ]
      }
    },
    cloned = clone( orig );


console.log(
  ( cloned.hasOwnProperty("foo") && "PASS" ) || "FAIL", cloned.foo
);
console.log(
  ( cloned.hasOwnProperty("inner") && "PASS" ) || "FAIL", cloned.inner
);
console.log(
  ( cloned.inner.hasOwnProperty("prop") && "PASS" ) || "FAIL", cloned.inner.prop
);
console.log(
  ( cloned.inner.hasOwnProperty("array") && "PASS" ) || "FAIL", cloned.inner.array
);

// Change a value of the original `inner.array`
cloned.inner.array[0] = "a";

console.log(
  ( orig.inner.array[0] !== cloned.inner.array[0] && "PASS" ) || "FAIL", 
    orig.inner.array[0], 
    cloned.inner.array[0]
);

cloned.foo = "qux";

console.log(
  ( orig.foo !== cloned.foo && "PASS" ) || "FAIL", orig.foo, cloned.foo
);

Demo & tests: http://jsfiddle.net/rwaldron/4SEGz/

Results in console