Javascript Object Inheritance-Code reuse ---For fun

典

Take a real scenario
With a javascript application to deal with transactions.
We can design a general object called "transaction", as parent object
Then design some other objects (invoice / stockreturn/ stockswap/stockadjust...), as child objects

parent object
var transaction={
        createdon:XXX,
        createdby:"xxxx",
        totalamount:"xxx"
        cal_gst:function(rate){
                this.totalamount*rate
        }
};

Child object
var invoice=inheritfrom(transaction)
invoice.setinvoiceno=function(){
        //some codes
        }

Then the invoice object has all the members as transaction has.

var stockreturn=inheritfrom(transaction)
stockreturn.stock_reusable=false...
Then the stockreturn object has all the members as transaction has.

典

At the moment no such function of  "inheritfrom"
There are a few ways to create this function
Let's show one
if (typeof Object.beget !== 'function') {
    Object.beget = function (o) {
              var F = function () {};
               F.prototype = o;
              return new F();
};
}
var invoice= Object.beget(transaction);

Also, we can write like this:

function object(o) {
       function F() {}
       F.prototype = o;
       return new F();
}


It's based on prototype , a hidden property of javascript object.
When create a child object, the child object's prototype point to the parent object

[ 本帖最后由 典 于 2011-2-9 11:12 编辑 ]

Dan.and.Andy

刚说这个 inheritfrom 没听说过啊, 你就又发出来了, 还是用prototype实现的.

典

原帖由 Dan.and.Andy 于 2011-2-9 11:14 发表
刚说这个 inheritfrom 没听说过啊, 你就又发出来了, 还是用prototype实现的.

before I read Douglas crockford's book I didn't know about the bloody prototype at all