如何使用JavaScript创建对象，以便以后可以访问它们的属性？

Question

I am filling an array with objects using this code:

    orders.push(getOrder(orderName, sender));
...
    function getOrder (orderName, sender){
    this.orderName = orderName;
    this.orderDate = new Date();
    this.sender = sender;

    console.log('Created order object.\n orderName: '+ orderName + '\n orderDate: ' + this.orderDate.getTime())}

When I try to access the objects in the array later on, I get an error message saying "Cannot read property 'orderDate' of undefined". Here is the code I use to access the objects:

dishEmitter.on('checkIfReady', function(){
    orders.forEach(function(order){
        console.log(order);
        var now = new Date();
        if(Math.abs((now.getTime() - order.orderDate.getTime()) / 1000) >= 5){
            broadcast('Your ' + order.orderName + ' is ready!', order.sender);
            orders.splice(indexOf(order),1);
        }
    })
})

I am writing a small sample application to learn a little about nodejs. All I want to do is create an order, and after 5 seconds, the order shall be ready (returning some message to the client who ordered)

I uploaded my full code in case anyone wants to look at it (some of the strings are in german though): server.js mensa.js

Answer 1

getOrder is not being used as a constructor, so the this reference actually points to a different object than what is being returned. Change it to function Order() and call it with orders.push( new Order() ) instead:

function Order(orderName, sender) {

    this.orderName = orderName;
    this.orderDate = new Date();
    this.sender    = sender;
}

Usage:

dishEmitter.on('order', function(orderName, sender){
    orders.push( new Order( orderName, sender ) );
})