它做五件事：
- 它创建一个新对象。这个对象的类型很简单 object。
- 它将这个新对象的内部不可访问的[[prototype]]（即__proto__）属性设置为构造函数的外部，可访问的原型对象（每个函数对象都会自动具有prototype属性）。
- 它使
this变量指向新创建的对象。
- 每当
this提及时，它将使用新创建的对象执行构造函数。
- 除非构造函数返回非
null对象引用，否则它将返回新创建的对象。在这种情况下，将返回该对象引用。
注意：构造函数指的是new关键字后面的函数，如
new ConstructorFunction(arg1, arg2)
完成此操作后，如果请求新对象的未定义属性，脚本将检查该对象的 改为 [[prototype]]对象的属性。这就是您可以获得类似于JavaScript中传统类继承的方法的方法。
关于这一点最困难的部分是点号2。每个对象（包括函数）都具有称为[[prototype]]的内部属性。它可以只被在创建对象的时间与设置，无论是新的，具有的Object.create，或者基于文本（函数默认Function.prototype的，数字到Number.prototype等）。只能使用Object.getPrototypeOf（someObject）读取它。有没有其他的方式来设置或读取此值。
函数除了隐藏的[[prototype]]属性外，还具有称为prototype的属性，您可以访问和修改此属性，以为您创建的对象提供继承的属性和方法。
这是一个例子：
ObjMaker = function() {this.a = 'first';};
// ObjMaker is just a function, there's nothing special about it that makes
// it a constructor.
ObjMaker.prototype.b = 'second';
// like all functions, ObjMaker has an accessible prototype property that
// we can alter. I just added a property called 'b' to it. Like
// all objects, ObjMaker also has an inaccessible [[prototype]] property
// that we can't do anything with
obj1 = new ObjMaker();
// 3 things just happened.
// A new, empty object was created called obj1. At first obj1 was the same
// as {}. The [[prototype]] property of obj1 was then set to the current
// object value of the ObjMaker.prototype (if ObjMaker.prototype is later
// assigned a new object value, obj1's [[prototype]] will not change, but you
// can alter the properties of ObjMaker.prototype to add to both the
// prototype and [[prototype]]). The ObjMaker function was executed, with
// obj1 in place of this... so obj1.a was set to 'first'.
obj1.a;
// returns 'first'
obj1.b;
// obj1 doesn't have a property called 'b', so JavaScript checks
// its [[prototype]]. Its [[prototype]] is the same as ObjMaker.prototype
// ObjMaker.prototype has a property called 'b' with value 'second'
// returns 'second'
就像类继承一样，因为现在，您使用的任何对象new ObjMaker()也似乎都继承了'b'属性。
如果您想要子类之类的东西，请执行以下操作：
SubObjMaker = function () {};
SubObjMaker.prototype = new ObjMaker(); // note: this pattern is deprecated!
// Because we used 'new', the [[prototype]] property of SubObjMaker.prototype
// is now set to the object value of ObjMaker.prototype.
// The modern way to do this is with Object.create(), which was added in ECMAScript 5:
// SubObjMaker.prototype = Object.create(ObjMaker.prototype);
SubObjMaker.prototype.c = 'third';
obj2 = new SubObjMaker();
// [[prototype]] property of obj2 is now set to SubObjMaker.prototype
// Remember that the [[prototype]] property of SubObjMaker.prototype
// is ObjMaker.prototype. So now obj2 has a prototype chain!
// obj2 ---> SubObjMaker.prototype ---> ObjMaker.prototype
obj2.c;
// returns 'third', from SubObjMaker.prototype
obj2.b;
// returns 'second', from ObjMaker.prototype
obj2.a;
// returns 'first', from SubObjMaker.prototype, because SubObjMaker.prototype
// was created with the ObjMaker function, which assigned a for us
在最终找到此页面之前，我读了很多有关此主题的垃圾，并用漂亮的图表很好地说明了这一点。