How to do page navigation for many, many pages? Logarithmic page navigation
What's the best way of displaying page navigation for many, many pages?
(Initially this was posted as a how-to tip with my answer included in the question. I've now split my answer off into the "answers" section below).
To be more specific:
Suppose you're displaying a set of records to the user, broken up into fixed-size pages (like the results of a Google search, for example). If there are only a few pages, you can display a page navigation area at the end of the results that might look like this:
[ << ] [<] 1 2 3 4 5 6 7 8 9 10 11 12 13 [ > ] [ >> ]
But this quickly becomes unweildy if there are much more than 20 or 30 pages of results.
Sometimes you'll see things like this:
[ << ] [<] ... 665 666 667 668 669 670 671 672 673 ... [ > ] [ >> ]
or this:
[ << ] [<] 1 2 3 ... 667 668 669 670 671 ... 845 846 847 [ > ] [ >> ]
but in both cases, navigating to anywhere in the middle of the "..." sections would take many, many mousclicks. Sometimes an input box for entering the page number directly is provided; otherwise (assuming we're talking about a webpage here) the savvy user is likely to look at the URL to see if they can edit it directly.
What would be nice would be to have a pagination display that lets the user reach any page in only a few mouseclicks, without having ridiculously many links.
How would that best be achieved?
Answer
Here's my solution - use "Logarithmic Page Navigation":
This can be achieved by having page numbers distributed logarithmically, according to distance from either the endpoints or the current page. Here's an example of what I mean:
1 2 3 4 5 6 . 10 . 20 . 30 . 40 . 50 .. 100 .. 200 . 210 . 220 . 230 . 240 . 250 . 252 253 254 255 256 257 258 259 260 261 262 . 270 . 280 . 290 . 300 . 310 .. 400 .. 500 .. 600 .. 700 .. 800 .. 900 .. 950 . 960 . 970 . 980 . 990 . 995 996 997 998 999 1000
Notice how in the gaps, numbering goes from 1s, to 10s, to 100s (etc.). (I use powers of 10, but in principle you could use a different scheme - powers of 2, say).
I wrote some code that does this back in 2004, and thought I'd share it here. There are PHP and ASP versions, but the logic ought to be simple to translate into any language. Note that the bit at the bottom (in both cases) just displays some examples. Obviously the formatting will need customization to match your webpage (or application), so it's pretty basic here. Alter LINKS_PER_STEP in paginationHTML to determine how many numbers get displayed before the step size increases, as you move away from the endpoints or current page.
For a more compact output you could also consider altering the code so that the numbering is not "dense" around the endpoints (i.e. dense only around the current page).
Here's the code:
PHP version:
<?
// Used by paginationHTML below...
function paginationLink($p, $page, $URL)
{
if ($p==$page) return '<b style="color:#C0C0C0">' . $p . '</b>';
return '<a href="' . $URL . $p . '">' . $p . '</a>';
}
// Used by paginationHTML below...
function paginationGap($p1, $p2)
{
$x = $p2-$p1;
if ($x==0) return '';
if ($x==1) return ' ';
if ($x<=10) return ' . ';
if ($x<=100) return ' .. ';
return ' ... ';
}
// URL requires the $page number be appended to it.
// e.g. it should end in '&page=' or something similar.
function paginationHTML($page, $lastPage, $URL)
{
$LINKS_PER_STEP = 5;
// Nav buttons
if ($page>1)
$result = '<form action="' . $URL . '1" method="POST" style="display:inline"><input type="submit" value=" |< "></form> ' .
'<form action="' . $URL . ($page-1) . '" method="POST" style="display:inline"><input type="submit" value=" < "></form>';
else $result = '<input type="button" value=" |< " disabled> <input type="button" value=" < " disabled>';
$result .= ' ' . $page . ' ';
if ($page<$lastPage)
$result .= '<form action="' . $URL . ($page+1) . '" method="POST" style="display:inline"><input type="submit" value=" > "></form> ' .
'<form action="' . $URL . $lastPage . '" method="POST" style="display:inline"><input type="submit" value=" >| "></form>';
else $result .= '<input type="button" value=" > " disabled> <input type="button" value=" >| " disabled>';
$result .= "<br>";
// Now calculate page links...
$lastp1 = 1;
$lastp2 = $page;
$p1 = 1;
$p2 = $page;
$c1 = $LINKS_PER_STEP+1;
$c2 = $LINKS_PER_STEP+1;
$s1 = '';
$s2 = '';
$step = 1;
while (true)
{
if ($c1>=$c2)
{
$s1 .= paginationGap($lastp1,$p1) . paginationLink($p1,$page,$URL);
$lastp1 = $p1;
$p1 += $step;
$c1--;
}
else
{
$s2 = paginationLink($p2,$page,$URL) . paginationGap($p2,$lastp2) . $s2;
$lastp2 = $p2;
$p2 -= $step;
$c2--;
}
if ($c2==0)
{
$step *= 10;
$p1 += $step-1; // Round UP to nearest multiple of $step
$p1 -= ($p1 % $step);
$p2 -= ($p2 % $step); // Round DOWN to nearest multiple of $step
$c1 = $LINKS_PER_STEP;
$c2 = $LINKS_PER_STEP;
}
if ($p1>$p2)
{
$result .= $s1 . paginationGap($lastp1,$lastp2) . $s2;
if (($lastp2>$page)||($page>=$lastPage)) return $result;
$lastp1 = $page;
$lastp2 = $lastPage;
$p1 = $page+1;
$p2 = $lastPage;
$c1 = $LINKS_PER_STEP;
$c2 = $LINKS_PER_STEP+1;
$s1 = '';
$s2 = '';
$step = 1;
}
}
}
?>
<br><br><br>
<?=paginationHTML(1,1,'?page=')?>
<br><br><br>
<?=paginationHTML(2,3,'?page=')?>
<br><br><br>
<?=paginationHTML(3,3,'?page=')?>
<br><br><br>
<?=paginationHTML(73,100,'?page=')?>
<br><br><br>
<?=paginationHTML(4,100,'?page=')?>
<br><br><br>
<?=paginationHTML(257,1000,'?page=')?>
<br><br><br>
<?=paginationHTML(7062,10555,'?page=')?>
<br><br><br>
<?=paginationHTML(22080,503456,'?page=')?>
ASP version:
<%
' Used by paginationHTML below...
Function paginationLink(p, page, URL)
if p=page then
paginationLink = "<b style=""color:#C0C0C0"">" & p & "</b>"
else
paginationLink = "<a href=""" & URL & p & """>" & p & "</a>"
end if
End Function
' Used by paginationHTML below...
Function paginationGap(p1, p2)
Dim x
x = p2-p1
if x=0 then
paginationGap = ""
elseif x=1 then
paginationGap = " "
elseif x<=10 then
paginationGap = " . "
elseif x<=100 then
paginationGap = " .. "
else
paginationGap = " ... "
end if
End Function
' URL requires the page number be appended to it.
' e.g. it should end in "&page=" or something similar.
Function paginationHTML(page, lastPage, URL)
const LINKS_PER_STEP = 5
Dim p1, p2, c1, c2, s1, s2, lastp1, lastp2, step
' Nav buttons
if page>1 then
paginationHTML = "<form action=""" & URL & "1"" method=""POST"" style=""display:inline""><input type=""submit"" value="" |< ""></form> " & _
"<form action=""" & URL & (page-1) & """ method=""POST"" style=""display:inline""><input type=""submit"" value="" < ""></form>"
else
paginationHTML = "<input type=""button"" value="" |< "" disabled> <input type=""button"" value="" < "" disabled>"
end if
paginationHTML = paginationHTML & " " & page & " "
if page<lastPage then
paginationHTML = paginationHTML & "<form action=""" & URL & (page+1) & """ method=""POST"" style=""display:inline""><input type=""submit"" value="" > ""></form> " & _
"<form action=""" & URL & lastPage & """ method=""POST"" style=""display:inline""><input type=""submit"" value="" >| ""></form>"
else
paginationHTML = paginationHTML & "<input type=""button"" value="" > "" disabled> <input type=""button"" value="" >| "" disabled>"
end if
paginationHTML = paginationHTML & "<br>"
' Now calculate page links...
lastp1 = 1
lastp2 = page
p1 = 1
p2 = page
c1 = LINKS_PER_STEP+1
c2 = LINKS_PER_STEP+1
s1 = ""
s2 = ""
step = 1
do
if c1>=c2 then
s1 = s1 & paginationGap(lastp1, p1) & paginationLink(p1, page, URL)
lastp1 = p1
p1 = p1+step
c1 = c1-1
else
s2 = paginationLink(p2, page, URL) & paginationGap(p2, lastp2) & s2
lastp2 = p2
p2 = p2-step
c2 = c2-1
end if
if c2=0 then
step = step*10
p1 = p1+step-1 ' Round UP to nearest multiple of step
p1 = p1-(p1 mod step)
p2 = p2-(p2 mod step) ' Round DOWN to nearest multiple of step
c1 = LINKS_PER_STEP
c2 = LINKS_PER_STEP
end if
if p1>p2 then
paginationHTML = paginationHTML & s1 & paginationGap(lastp1, lastp2) & s2
if (lastp2>page) or (page>=lastPage) then exit do
lastp1 = page
lastp2 = lastPage
p1 = page+1
p2 = lastPage
c1 = LINKS_PER_STEP
c2 = LINKS_PER_STEP+1
s1 = ""
s2 = ""
step = 1
end if
loop
End Function
%>
<br><br><br>
<%=paginationHTML(1,1,"?page=")%>
<br><br><br>
<%=paginationHTML(2,3,"?page=")%>
<br><br><br>
<%=paginationHTML(3,3,"?page=")%>
<br><br><br>
<%=paginationHTML(73,100,"?page=")%>
<br><br><br>
<%=paginationHTML(4,100,"?page=")%>
<br><br><br>
<%=paginationHTML(257,1000,"?page=")%>
<br><br><br>
<%=paginationHTML(7062,10555,"?page=")%>
<br><br><br>
<%=paginationHTML(22080,503456,"?page=")%>
Javascript version (within complete test page):
<!doctype html>
<html>
<head>
<title>Logarithmic Pagination Demo</title>
<style>
body {background:#C0C0C0;font-family:Arial,Helvetica,sans-serif;font-size:16px;text-align:left}
div {margin:0;padding:0}
div#setupDiv {margin:40px;text-align:center}
table#datarows {border-collapse:collapse;margin:40px auto}
table#datarows th {padding:5px 10px;background:#80B0FF;color:#FFFFFF;border:2px solid #80B0FF;width:1000px;text-align:center}
table#datarows td {padding:2px 10px;background:#FFFFFF;color:#D0D0D0;border:2px solid #80B0FF;width:1000px;text-align:left;font-style:italic}
input.err {border:2px solid #FF0000;background-color:#FFF0F0}
form.pager {display:table;margin:0 auto;padding:20px;border:2px solid #E0E0E0;border-radius:10px;background-color:#D0D0D0;text-align:left;white-space:nowrap}
form#pager1 {margin-top:40px}
form#pager2 {margin-bottom:60px}
form.pager div {display:table-cell;vertical-align:middle;padding:0 20px;white-space:nowrap}
form.pager div + div {border-left:2px solid #E0E0E0}
form.pager div.plinks {padding:0;border:0 none;font-size:14px;line-height:24px;max-width:800px;white-space:normal}
form.pager div.plinks b {display:inline-block;vertical-align:bottom;font-size:24px;line-height:21px;height:24px;overflow:hidden;color:#808080}
form.pager div.plinks a {text-decoration:none;color:black}
form.pager div.plinks a:hover {color:#0000FF;font-weight:bold}
form.pager div.plinks + div {border:0 none}
</style>
<script>
var NumPages, RecsPerPage, els1, els2, plinks1, plinks2;
function setupClick()
{
var el, n, r;
el = document.getElementById("NumPages");
el.className = ((n = (el.value >>> 0)) ? "" : "err");
el = document.getElementById("RecsPerPage");
el.className = ((r = (el.value >>> 0)) ? "" : "err");
if (n&&r) { NumPages = n; RecsPerPage = r; setupServerPage(); }
}
// This function sets up what would normally be part of the server's HTML output.
function setupServerPage()
{
var totRecs = NumPages * RecsPerPage, tbdy = document.getElementById("datarows").tBodies[0], l = tbdy.rows.length;
document.getElementById("plength1").innerHTML = document.getElementById("plength2").innerHTML = totRecs + " record" + ((totRecs===1)?"":"s") + "<br>" + NumPages + " page" + ((NumPages===1)?"":"s");
els1["pcount"].value = els2["pcount"].value = NumPages;
while (l>RecsPerPage) tbdy.deleteRow(--l);
while (l<RecsPerPage) tbdy.insertRow(l++).insertCell(0).innerHTML = "Some data...";
pageNavigate(1);
}
// This would be handled by a return trip to the server, if not using AJAX.
function pageClick(e)
{
e = e||window.event;
var s = e.target||e.srcElement, n, p, el;
if (s.tagName==="A") { n = (p = s.href).lastIndexOf("=")+1; pageNavigate(p.substring(n) >>> 0); return false; }
else if ((s.tagName!=="INPUT")||(s.type!=="submit")) return;
if (!(n = s.name)) { p = ((el = this.elements["p"]).value >>> 0); if ((p<=0)||(p>NumPages)) { el.className = "err"; return false; }}
else if (n==="p1") p = 1;
else if (n==="pprev") p = (this.elements["pcurr"].value >>> 0)-1;
else if (n==="pnext") p = (this.elements["pcurr"].value >>> 0)+1;
else if (n==="plast") p = (this.elements["pcount"].value >>> 0);
pageNavigate(p);
return false;
}
// This would also be handled by a return trip to the server, or else data records could be retrieved via AJAX.
function pageNavigate(p)
{
els1["p"].className = els2["p"].className = els1["p"].value = els2["p"].value = "";
if (p<1) p = 1; else if (p>NumPages) p = NumPages;
els1["p1"].disabled = els2["p1"].disabled = els1["pprev"].disabled = els2["pprev"].disabled = (p===1);
els1["pnext"].disabled = els2["pnext"].disabled = els1["plast"].disabled = els2["plast"].disabled = (p===NumPages);
els1["pcurr"].value = els2["pcurr"].value = p;
// if the server is handling this, insert NON-logarithmic page links here (can be just first, current, and last page).
plinks1.innerHTML = plinks2.innerHTML = logarithmicPaginationLinks(NumPages,p,"?p=");
}
// This function produces the logarithmic pagination links.
function logarithmicPaginationLinks(lastPage,matchPage,linkURL)
{
function pageLink(p, page) { return ((p===page) ? "<b>"+p+"</b>" : '<a href="'+linkURL+p+'">'+p+"</a>"); }
function pageGap(x) { if (x===0) return ""; if (x===1) return " "; if (x<=10) return " . "; if (x<=100) return " .. "; return " ... "; }
var page = (matchPage ? matchPage : 1), LINKS_PER_STEP = 5, lastp1 = 1, lastp2 = page, p1 = 1, p2 = page, c1 = LINKS_PER_STEP+1, c2 = LINKS_PER_STEP+1, s1 = "", s2 = "", step = 1, linkHTML = "";
while (true)
{
if (c1>=c2)
{
s1 += pageGap(p1-lastp1) + pageLink(p1,matchPage);
lastp1 = p1;
p1 += step;
c1--;
}
else
{
s2 = pageLink(p2,matchPage) + pageGap(lastp2-p2) + s2;
lastp2 = p2;
p2 -= step;
c2--;
}
if (c2===0)
{
step *= 10;
p1 += step-1; // Round UP to nearest multiple of step
p1 -= (p1 % step);
p2 -= (p2 % step); // Round DOWN to nearest multiple of step
c1 = LINKS_PER_STEP;
c2 = LINKS_PER_STEP;
}
if (p1>p2)
{
linkHTML += s1 + pageGap(lastp2-lastp1) + s2;
if ((lastp2>page)||(page>=lastPage)) break;
lastp1 = page;
lastp2 = lastPage;
p1 = page+1;
p2 = lastPage;
c1 = LINKS_PER_STEP;
c2 = LINKS_PER_STEP+1;
s1 = '';
s2 = '';
step = 1;
}
}
return linkHTML;
}
window.onload = function()
{
els1 = document.getElementById("pager1").elements;
els2 = document.getElementById("pager2").elements;
plinks1 = document.getElementById("plinks1");
plinks2 = document.getElementById("plinks2")
document.getElementById("pager1").onclick = document.getElementById("pager2").onclick = pageClick;
(document.getElementById("setupDiv").lastChild.onclick = setupClick)();
}
</script>
</head>
<body>
<div id="setupDiv">Select number of pages: <input type="text" id="NumPages" value="100" size="7"> and records per page: <input type="text" id="RecsPerPage" value="20" size="7"> <input type="button" value=" Go "></div>
<hr>
<form id="pager1" class="pager" method="GET"><input type="hidden" name="pcount" value=""><input type="hidden" name="pcurr" value="1">
<div>Go to page: <input type="text" name="p" size="7"> <input type="submit" value=" Go "></div>
<div><input type="submit" name="p1" value=" |< " disabled> <input type="submit" name="pprev" value=" < " disabled></div>
<div id="plinks1" class="plinks"></div>
<div><input type="submit" name="pnext" value=" > "> <input type="submit" name="plast" value=" >| "></div>
<div id="plength1"></div>
</form>
<table id="datarows"><thead><tr><th>Column Heading...</th></tr></thead><tbody></tbody></table>
<form id="pager2" class="pager" method="GET"><input type="hidden" name="pcount" value=""><input type="hidden" name="pcurr" value="1">
<div>Go to page: <input type="text" name="p" size="7"> <input type="submit" value=" Go "></div>
<div><input type="submit" name="p1" value=" |< " disabled> <input type="submit" name="pprev" value=" < " disabled></div>
<div id="plinks2" class="plinks"></div>
<div><input type="submit" name="pnext" value=" > "> <input type="submit" name="plast" value=" >| "></div>
<div id="plength2"></div>
</form>
</body>
</html>