How can this Javascript variable have value?

Question

I got this JavaScript code on my webpage:

var dLastUpdate = new Date;

var getData = function () {
   alert(dLastUpdate);
   $.post("mypage.aspx?accion=getData", {}, function (data) {RefreshData(data)})
}

function RefreshData(rValue) {    
   dLastUpdate = rValue.UpdateTime;
}

getData function it's called many times. In theory, dLastUpdate should be empty the first call, and save the value returned from server. Never the less, in the alert(dLastUpdate); the variable already have value on the first call (page load).

How can this be posible?

Could be that the client is caching the value from previous run? Thanks!

Sounds like the everyday ajax problem http://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-asynchronous-call — elclanrs, Mar 02 '15 at 21:47
Why wouldn't it have a value, it's set to the current date at instantiation ? — adeneo, Mar 02 '15 at 21:47
You set it right here: `var dLastUpdate = new Date;`. So of course it has a value. Presumably you meant to just do `var dLastUpdate;` and leave it undefined? — Matt Burland, Mar 02 '15 at 21:47
@elclanrs Actually the problem is entirely independent of the Ajax call. — Paul Roub, Mar 02 '15 at 21:48

score 4 · Accepted Answer · answered Mar 02 '15 at 21:47

4

You initialise it and give it a value on line 1.

var dLastUpdate = new Date;

That doesn't depend on the Ajax call being processed.

answered Mar 02 '15 at 21:47

Quentin

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Haaa I didn't know that! I have the idea that i was creating a variable of date tipe, no givin it a value! – ericpap Mar 02 '15 at 22:01
1

@ericpap: JS is dynamically typed. Variables don't have a type, only values do. – Felix Kling Mar 02 '15 at 22:05

How can this Javascript variable have value?

1 Answers1