Question

我对 Java版原型的使用感到困惑不解。

举以下例子:

(1)

   function Rectangle(w, h) { 
      this.width=w; 
      this.height=h; 
      this.area=function() { this.width * this.height; }
   }

And a similar case where the area is attached to a prototype as follows:

(2)

   function Rectangle(w, h) { 
      this.width=w; 
      this.height=h; 
   }
   Rectangle.prototype.area=function() { this.width * this.height; }

What is the diffrence between (1) and (2) ?
When would you use (1) or (2) for writing methods on classes?

Answer 1

prototypes are best shown differently.

function rectangle(w, h) {
    var rect = {};
    rect.width=w; 
    rect.height=h; 
    rect.area=function() { return this.width * this.height; };
    return rect;
}

vs

var Rectangle = {
    area: function() { return this.width * this.height; }
}

function rectangle(w, h) {
    var rect = Object.create(Rectangle);
    rect.width=w; 
    rect.height=h; 
    return rect;
}

这一概念很简单,你把共同点放在原型上,然后继承。

你们何时想要使用原型? 途径。

当然,你可能希望。改善ES5 OO 食糖

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