JavaScript prototype in the use of detailed knowledge _ basics

First look at the following code:

function Machine (Ecode, horsepower) {
  this.ecode = Ecode;
  This.horsepower = horsepower;
}

function ShowMe () {
  alert (this.name + "" + This.ecode + "" + This.horsepower);
}

var machine = new Machine ("Code1");
Machine.name = "Machine1";
Machine.showme = ShowMe;
Machine.showme ();

Such a piece of code, although the establishment of a machine object, through the MACHINE.SHOWME = ShowMe, so that the SHOWME function into a machine object machine method.

However, just look at the above two functions (one is the constructor of the object, one is the normal method) has no relation, such code, not so "elegant", therefore, there is prototype.

Machine
function Machine (ecode, horsepower) {
  this.ecode = Ecode;
  This.horsepower = horsepower;
}
Pay special attention to this sentence, Machine.prototype is initialized at the first time,
//When the Machine is invoked as a constructor, the engine value is not changed
Machine.prototype.engine = This.ecode + "" + This.horsepower;
Machine.prototype.showme = function () {alert (THIS.name + "" + This.ecode + "" + This.horsepower);}

Using the above code, all the machine objects have a ShowMe method.

But pay special attention to:

Prototype is only faced with instances, not with class objects. (JS, the class itself is an object) so Machine.showme (), will report the error, because machine this object is not ShowMe method.

So, how do we use the ShowMe method? A new machine instance must be created, and only the machine instance will have this method.

var machine = new Machine ("Code1");
Machine.name = "Machine1";
Machine.showme (); Output Machine1 code1 15.

With prototype, we are more likely to implement inheritance relationships. For example, I now write a car class, need to inherit the current machine class, just write the following code can be:

Cars
Function car (name, Ecode, horsepower) {
  this.name = name;
  Invokes the constructor of the parent class so that the object of the car has ecode, horsepower property
  Machine.call (this, ecode, horsepower);
The car's prototype points to Machine so that the car object has any properties and methods for the Machine prototype, such as showme
car.prototype = new Machine ();

Here's how to invoke the parent constructor, and how to get the prototype of the parent class, and the annotations are clear, not to be discussed.

Then, we can create a new object to test:

The object that creates a new class car.
var Xiali = new Car ("Xiali", "AAA",);
alert (xiali.engine);
Xiali.showme ();

Above, is the basic application of prototype, but also is the most important application of prototype.

Master of the use of prototype, in the future process, for the construction and inheritance of objects, there will be a deeper understanding.

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