我的功能无法运行？

Question

I'm getting tired of firebug telling my vars aren't defined...

I have a button: next. When the button is clicked, I want it to load a php page into a div, assigning the php page the variable representing the next page.

To do this, I have a variable crntpage that stores the value of the current page. In order to calculate what the var for the next page must be I have a function called next which calculates the value and returns it.

Let's assume that we are on page 5:

javascript

$(document).ready(function() {

$.ajax({
    url: 'pagination.php',
    type: 'POST',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    async: true,
    cache: false,
    success: function (pages) {
                last = pages['last'];
                crntpage = 1;

                function nxt(b) {
                    if (b == last) {
                        next  = last;
                    } else {
                        next = b + 1;
                    }
                    return next;
                }

                $('#next').live('click', function() {
                    crntpage(next);
                    $('#content').load('getposts.php?pagenum=' + nxt(crntpage));
                    return false;
                });
    }
});
});

html

<div id="previous"> 
        <a href=''> <-Previous</a>
</div>

I keep getting an error saying that next isn't defined. My guess is because my nxt function is not receiving the value of last. What am I doing wrong?

Answer 1

What you are trying to do with the nxt function can be accomplished more idiomatically with Math.min() :

$('#next').live('click', function() {
    crntpage = Math.min(crntpage + 1, last);
    $('#content').load('getposts.php?pagenum=' + crntpage);
    return false;
});

You should also prefix variable declarations with the var keyword, so as not to pollute the global namespace.

Here's the revised code together:

$(function() {

    var currentPage = 1;
    var last = 1;

    $('#next').live('click', function() {
        currentPage = Math.min(currentPage + 1, last);
        $('#content').load('getposts.php?pagenum=' + currentPage);
        return false;
    });

    $.ajax({
        url: 'pagination.php',
        type: 'POST',
        contentType: "application/json; charset=utf-8",
        dataType: "json",    
        cache: false,
        success: function (pages) {
            last = pages['last'];
        }
    });

});

Answer 2

It looks like you didn't define next . (or maybe it is defined in the part of your code that you didn't post here, I don't know) Have you tried this:

$(document).ready(function() {
var next = ''; //defining the variable first, then you set it below in nxt()
$.ajax({
    url: 'pagination.php',
    type: 'POST',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    async: true,
    cache: false,
    success: function (pages) { 
                last = pages['last'];
                crntpage = 1;

                function nxt(b) {
                    if (b == last) {
                        next  = last;
                    } else {
                        next = b + 1;
                    }
                    return next;
                }

                $('#next').live('click', function() {
                    crntpage(next);
                    $('#content').load('getposts.php?pagenum=' + nxt(crntpage));
                    return false;
                });
    }
});
});