JavaScript Design Patterns and open practice learning (a) JavaScript implementation polymorphism

Or a duck singing, for Example.

1. Prototype add methods or properties to an object

<script>varMakesound=function(animal) {animal.sound (); }        varduck=function() {} Duck.prototype.sound=function() {console.log ("quack"); }        varchichen=function() {} Chichen.prototype.sound=function() {console.log ("giggle"); } makesound (NewChichen ()); MakeSound (NewDuck ())</script>

Methods for adding sound to defined duck and chicken

2, typeof and Instanceof usage

Only animals with sound methods can sing.

1) typeof

Used to detect the data type of a given variable, the possible return value:

1. ' Undefined '---this value is undefined;

2. ' Boolean '---this value is a Boolean value;

3. ' String '---this value is a string;

4. ' Number '---this value is numeric;

5. ' Object '---this value is an object or null;

6. The ' function '---this value is a functional.

var makesound=function  (animal) {            if(typeof animal.sound=== ' function ') {                animal.sound ();            }}

2) instanceof is used to determine whether an object is the strength of another object, the return value TRUE or False

var makesound=function  (animal) {            ifinstanceof  Function) {                animal.sound ();            }}

JavaScript Design Patterns and open practice learning (a) JavaScript implementation polymorphism