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JavaScript

// ISUSEROBJECT DETECTION
//
// By Steven de Salas
// http://www.desalasworks.com
// 
// CC Attribution Share-Alike Licence 3.0
// http://creativecommons.org/licenses/by-sa/3.0/

function isUserObject(obj) {

    // Should be an instance of an Object
    if (!(obj instanceof Object)) return false;

    // Should have a constructor that is an instance of Function
    if (typeof obj.constructor === 'undefined') return false;
    if (!(obj.constructor instanceof Function)) return false;

    // Avoid built-in functions and type definitions
    if (obj instanceof Function && 
      Function.prototype.toString.call(obj).indexOf('[native code]') > -1) 
          return false;
    
    return true;
}

// ASSERT HELPER FUNCTION

var n = 0;
function assert(condition, message) {
    n++;
    if (condition !== true) {
       document.write(n + '. FAILS: ' + (message || '(no message)') + '<br/>');
    } else {
       document.write(n + '. PASS: ' + (message || '(no message)') + '<br/>');
    }
}

// USER CREATED OBJECTS

assert(isUserObject({}), '{} -- Plain object');
assert(isUserObject(function() {}), 'function() {} -- Plain function');
assert(isUserObject([]), '[] -- Plain array');

assert(isUserObject(/regex/), '/regex/ - Native regex');
assert(isUserObject(new Date()), 'new Date() - Native date object through instantiation');

assert(isUserObject(new String('string')), 'new String("string") - Native string object through instantiation');
assert(isUserObject(new Number(1)), 'new Number(1) - Native number object through instantiation');
assert(isUserObject(new Boolean(true)), 'new Boolean(true) - Native boolean object through instantiation');
assert(isUserObject(new Array()), 'new Array() - Native array object through instantiation');
assert(isUserObject(new Object()), '{} -- new Object() - Native object through instantiation');
assert(isUserObject(new Function('alert(1)')), '{} -- Native function through instantiation');

// USER OBJECT INSTANTIATION AND INHERITANCE

var...