Question

var events = [
    {id: 100,url: "mc.jsp?id=" + id},
    {id: 200,url: "mc2.jsp?id=" + id},
    {id: 300,url: "mc2.jsp?id=" + id}
]

When run, the url equals mc.jsp?id=undefined,
so how can assign the id (100) to the url to get the value of mc.jsp?id=100?
And also make the second url as mc2.jsp=200 and third one mc2.jsp？id=300
so I cannot make assignment outside the array.

Answer 1

You can’t access other properties in an object literal on constructions. You get an undefined because you have no variable id. You will need to use:

var id = 100;
var events = [{"id":id, "url":"mc.jsp?id=" + id}];

or:

var event = {id: 100};
event.url = "mc.jsp?id=" + event.id
var events = [event];

but you could define a getter:

var events = [{id: 100, get url() { return "mc.jsp?id="+this.id; } }];

which is very complicated and difficult to understand. Maybe it’s better to do something like this:

function MyEvent(id, mc) {
    this.id = id;
    this.mc = mc;
}
MyEvent.prototype.getUrl = function() {
    return "mc"+this.mc+".jsp?id="+this.id;
};

var events = [new MyEvent(100, ""), new MyEvent(200, "2"), ...];

However, there should be no such problem. If you hardcode the numbers, why don’t you hardcode the urls? If you don’t want the redundancy, just don’t store the id two times and append it each time you need it.