js小结

1）Closures 闭包

 

var x = function() {
    var i = 0;
    return function() {
        return ++i;
    }
};

var f = x();
document.write("first: " + f());
document.write(", second: " + f());

2）Polymorphism 多态性

 

 

var animal = function() {
    var legs = 4;
    var nipples = 2;
    this.getLegs = function() { return legs; };
    this.getNipples = function() { return nipples; };
};
var dog = function() {
    animal.call(this);
    this.getNipples = function() { return 8; };
}
var human = function() {
    animal.call(this);
    this.getLegs = function() { return 2; };
}
var lassie = new dog();
var hubert = new human();

document.write("dog: " + lassie.getLegs() + "/" + lassie.getNipples());
document.write(", human: " + hubert.getLegs() + "/" + hubert.getNipples());

3）Call

 

 

var blog = function() {
    this.type = "blog";
    this.getType = function() {
        return this.type;
    }
}
var joshuasBlog = new blog();

document.write(joshuasBlog.getType() + "->" + joshuasBlog.getType.call({ type: "hehehe" }));

4）Prototype 原型

 

 

var y = function(value) {
    this.superValue = value;
    this.getSuperValue = function() { return this.superValue; }
}
var x = function(value) {
    this.value = value;
    this.getValue = function() { return this.value; }
}
x.prototype = new y(123);
var a = new x(1);
var b = new x(2);
document.write("a.value: " + a.getValue());
document.write(", b.value: " + b.value);
document.write(", a.superValue: " + a.getSuperValue());
document.write(", b.superValue: " + b.superValue);

答案：

 

 

Closures:
first: 1, second: 2 
Polymorphism:
dog: 4/8, human: 2/2 
Call:
blog->hehehe 
Prototype
a.value: 1, b.value: 2, a.superValue: 123, b.superValue: 123