javascript原型链继承用法实例分析

本文实例分析了javascript原型链继承的用法。。具体分析如下：

function Shape(){ 
 this.name = 'shape'; 
 this.toString = function(){ 
  return this.name; 
 } 
} 
 
function TwoDShape(){ 
 this.name = '2D shape'; 
} 
function Triangle(side,height){ 
 this.name = 'Triangle'; 
 this.side = side; 
 this.height = height; 
 this.getArea = function(){ 
  return this.side*this.height/2; 
 }; 
} 
 
/* inheritance */ 
TwoDShape.prototype = new Shape(); 
Triangle.prototype = new TwoDShape(); 

当我们对对象的prototype属性进行完全重写时，有时候会对对象constructor属性产生一定的负面影响。
所以，在我们完成相关的继承关系设定后，对这些对象的const属性进行相应的重置是一个非常好的习惯。如下所示：

TwoDShape.prototype.constructor = TwoDShape; 
Triangle.prototype.constructor = Triangle;

改写：
function Shape(){} 
 
Shape.prototype.name = 'shape'; 
Shape.prototype.toString = function(){ 
 return this.name; 
} 
 
function TwoDShape(){} 
 
TwoDShape.prototype = new Shape(); 
TwoDShape.prototype.constructor = TwoDShape; 
 
TwoDShape.prototype.name = '2d shape'; 
 
function Triangle(side,height){ 
 this.side = side; 
 this.height = height; 
} 
 
Triangle.prototype = new TwoDShape; 
Triangle.prototype.constructor = Triangle; 
 
Triangle.prototype.name = 'Triangle'; 
Triangle.prototype.getArea = function(){ 
 return this.side*this.height/2; 
}

再改写（引用传递而不是值传递）：
function Shape(){} 
 
Shape.prototype.name = 'shape'; 
Shape.prototype.toString = function(){ 
 return this.name; 
} 
 
function TwoDShape(){} 
 
TwoDShape.prototype = Shape.prototype; 
TwoDShape.prototype.constructor = TwoDShape; 
 
TwoDShape.prototype.name = '2d shape'; 
 
function Triangle(side,height){ 
 this.side = side; 
 this.height = height; 
} 
 
Triangle.prototype = TwoDShape.prototype; 
Triangle.prototype.constructor = Triangle; 
 
Triangle.prototype.name = 'Triangle'; 
Triangle.prototype.getArea = function(){ 

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