what is javascript uber

javascript uber is a method used in early javascript to let a method call the parent class. The uber method is similar to Java's super.

The operating environment of this article: Windows 7 system, JavaScript version 1.8.5, DELL G3 computer.

javascriptWhat is uber?

In early JavaScript, the uber method is similar to Java's super, which allows a method to call the method of the parent class. Douglas Crockford used the German "über", which means something similar to super, to avoid conflict with reserved words.

However, Crockford also said that the idea of ​​super is very important in the classic design pattern, but it seems unnecessary in the prototype and function design patterns of JavaScript. Classical Inheritance in JavaScript Classic object-oriented languages ​​generally have special syntax for accessing the parent class (super class), so that the methods of the subclass can use the methods of the parent class, and the methods of the subclass and the parent class have the same name. In modern JavaScript, there is no such special syntax. Uber can implement this function, but it is more cumbersome. Look at the following example:

// inheritance helper
function extend(Child, Parent) {
  var F = function () {};
  F.prototype = Parent.prototype;
  Child.prototype = new F();
  Child.prototype.constructor = Child;
  Child.uber = Parent.prototype;
}
// define -> augment
function Shape() {}
Shape.prototype.name = 'Shape';
Shape.prototype.toString = function () {
  return this.constructor.uber
  ? this.constructor.uber.toString() + ', ' + this.name
  : this.name;
};
// define -> inherit -> augment
function TwoDShape() {}
extend(TwoDShape, Shape);
TwoDShape.prototype.name = '2D shape';
// define
function Triangle(side, height) {
  this.side = side;
  this.height = height;
}
// inherit
extend(Triangle, TwoDShape);
// augment
Triangle.prototype.name = 'Triangle';
Triangle.prototype.getArea = function () {
  return this.side * this.height / 2;
};

Input in the Console:

var my = new Triangle(5, 10);
my.toString();

Output: "Shape, 2D shape, Triangle"

The derived level is: Shape -> TwoDShape -> Triangle

The extend function encapsulates the inherited code.

The role of the temporary constructor F(): when the properties of the subclass change, the properties of the parent class are not changed.

uber attribute: points to the parent class prototype.

In the toString() method, check whether the prototype of the parent class of the constructor exists. If it exists, call its toString() method, thereby realizing calling the parent class method in the subclass.

Recommended study: "javascript basic tutorial"

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