How to pass JavaScript variable to jQuery ajax request

Question

I am trying to pass a variable to an jquery ajax request:

$(document).ready(function() {
            // get page number
            var page = parseInt(getUrlParameter('page'));
            if (page < 1) page = 1;
            var page_next = page + 1;

          $.ajax({
                type: "GET",
                data: { 
                    page: page,

                },  
                dataType: 'json', 
           ...

unfortunatelly the variable "page" seems not to be present inside the ajax request. Doing an cosole.log(page); inside reveils "NaN" as a value.

The problem seems to be

if (page < 1) page = 1;

If this value retrieved via get is not present, then page will be NoN.

How can I make sure page is always defined as minimum 1 ?

the approach is absolutely correct, the error is probably in the function `getUrlParameter('page')`, which is NOT returning a valid response (or not a number or anything that can be converted to such). Can you please show us that function? — briosheje, Jun 09 '15 at 16:22
The only problem with the approach, from the code you've shared so far, is that [you don't have a radix on parseInt](http://stackoverflow.com/questions/6611824/why-do-we-need-to-use-radix), but that wouldn't cause this issue. Whatever `getUrlParameter` is returning is, as briosheje said, not something that can be converted to a number, hence: NaN: Not a Number — Quentin, Jun 09 '15 at 16:24
the problem seems to be with getURLParameter function as the guys above have pointed out. try with var page = 1; and see if variable contains value 1. — man_luck, Jun 09 '15 at 16:29
Just narrowed the error down. The problem is within: if (page < 1) page = 1; This does not seem to work if there is no get parameter "page". Will edit question now. — merlin, Jun 09 '15 at 16:41
@merlin please check my answer, I've suggested a validation in order to default the page to 1 if you get a Nan. — taxicala, Jun 09 '15 at 16:50

score 1 · Accepted Answer · answered Jun 09 '15 at 16:28

1

Your getUrlParameter is returning something that is not convertible to a number NaN = Not a Number, if you share that function maybe we can debug a little bit further the root cause of your issue, in the meantime, I suggest the following validation:

var page = parseInt(getUrlParameter('page'));
if (page < 1 || isNaN(page)) page = 1;
var page_next = page + 1;

That way if your page is not a number, you default it to page 1. Hope this clears things out and helps you.

answered Jun 09 '15 at 16:28

taxicala

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That's fine, but I would rather say that he should fix the getUrlParameter instead of its result. I mean, the result should already be a number, so he should assert that in the **function** rather than after it, especially from the moment that we have no idea of how / where he is taking such data from, right? – briosheje Jun 09 '15 at 16:31
Thats why i've edited my question. If He does not share the function there is no way to find the root cause, so I've only made a suggestion in order to make the code more robust. If a user types anything in the url other than a number, it would be nice that the application loads page 1 instead of crashing or displaying an error. – taxicala Jun 09 '15 at 16:33
This leads in the right direction. Works if I leave parseInt inside. If I remove it, the page+1 reveals 11 instead of 2. – merlin Jun 09 '15 at 17:03
You should leave parseInt in order to make it more robust. And the condition i've wrote is a safe check to default the page to 1 if the user types anything other than a number in the url. – taxicala Jun 09 '15 at 17:05

score 1 · Answer 2 · answered Jun 09 '15 at 16:51

If your problem is within the if statement, the fastest solution I can think about (despite I don't approve it) is this one:

Replace :

var page = parseInt(getUrlParameter('page'));

with:

var page = +getUrlParameter("page") || 1;

if page is falsey (NaN is falsey) it will set it to 1, else to its result.

Example with fiddle:

function getUrlParameter ( param ) {
    return param === "page" ? 5 : false;
}

var page = +getUrlParameter("hello") || 1;
alert(page);

page = +getUrlParameter("page") || 1;
alert(page);

http://jsfiddle.net/51tvdsve/

In any case, you should rather try to fix your getUrlParameter function instead of trying to avoid its output, but that's just my opinion.

How to pass JavaScript variable to jQuery ajax request

2 Answers2