JavaScript を使用して Blogger にページネーションを追加する方法
## 参考
[How to Add Numbered Page Navigation Widget for Blogger - Helplogger](https://helplogger.blogspot.jp/2014/04/how-to-add-numbered-page-navigation-widget-for-blogger.html)
## 使用方法
テーマ -> カスタマイズ -> 上級者向け -> CSS を追加
にページネーション用の CSS を追加する（参考サイトでは 7 種類の CSS があります）
```css
#blog-pager{clear:both;margin:30px auto;text-align:center; padding: 7px;}
.blog-pager {background: none;}
.displaypageNum a,.showpage a,.pagecurrent{font-size: 14px;padding: 5px 12px;margin-right:5px; color: #666; background-color:#eee;}
.displaypageNum a:hover,.showpage a:hover, .pagecurrent{background:#359BED;text-decoration:none;color: #fff;}
#blog-pager .pagecurrent{font-weight:bold;color: #fff;background:#359BED;}
.showpageOf{display:none!important}
#blog-pager .pages{border:none;}
```
テーマ -> HTML の編集
で </body> タグの直前にページネーションウィジェットを追加する
```html
<b:if cond='data:blog.pageType != "item"'>
<b:if cond='data:blog.pageType != "static_page"'>
<script type='text/javascript'>
/*<![CDATA[*/
/* 諸設定 */
var perPage=3;
var numPages=3;
var firstText ='First';
var lastText ='Last';
var prevText ='« Previous';
var nextText ='Next »';
var urlactivepage=location.href;
var home_page="/";
if(typeof firstText=="undefined")firstText="First";if(typeof lastText=="undefined")lastText="Last";var noPage;var currentPage;var currentPageNo;var postLabel;pagecurrentg();function looppagecurrentg(pageInfo){var html='';pageNumber=parseInt(numPages / 2);if(pageNumber==numPages-pageNumber){numPages=pageNumber*2+1}
pageStart=currentPageNo-pageNumber;if(pageStart<1)pageStart=1;lastPageNo=parseInt(pageInfo / perPage)+1;if(lastPageNo-1==pageInfo / perPage)lastPageNo=lastPageNo-1;pageEnd=pageStart+numPages-1;if(pageEnd>lastPageNo)pageEnd=lastPageNo;html+="<span class='showpageOf'>Page "+currentPageNo+' of '+lastPageNo+"</span>";var prevNumber=parseInt(currentPageNo)-1;if(currentPageNo>1){if(currentPage=="page"){html+='<span class="showpage firstpage"><a href="'+home_page+'">'+firstText+'</a></span>'}else{html+='<span class="displaypageNum firstpage"><a href="/search/label/'+postLabel+'?&max-results='+perPage+'">'+firstText+'</a></span>'}}
if(currentPageNo>2){if(currentPageNo==3){if(currentPage=="page"){html+='<span class="showpage"><a href="'+home_page+'">'+prevText+'</a></span>'}else{html+='<span class="displaypageNum"><a href="/search/label/'+postLabel+'?&max-results='+perPage+'">'+prevText+'</a></span>'}}else{if(currentPage=="page"){html+='<span class="displaypageNum"><a href="#" onclick="redirectpage('+prevNumber+');return false">'+prevText+'</a></span>'}else{html+='<span class="displaypageNum"><a href="#" onclick="redirectlabel('+prevNumber+');return false">'+prevText+'</a></span>'}}}
if(pageStart>1){if(currentPage=="page"){html+='<span class="displaypageNum"><a href="'+home_page+'">1</a></span>'}else{html+='<span class="displaypageNum"><a href="/search/label/'+postLabel+'?&max-results='+perPage+'">1</a></span>'}}
if(pageStart>2){html+=' ... '}
for(var jj=pageStart;jj<=pageEnd;jj++){if(currentPageNo==jj){html+='<span class="pagecurrent">'+jj+'</span>'}else if(jj==1){if(currentPage=="page"){html+='<span class="displaypageNum"><a href="'+home_page+'">1</a></span>'}else{html+='<span class="displaypageNum"><a href="/search/label/'+postLabel+'?&max-results='+perPage+'">1</a></span>'}}else{if(currentPage=="page"){html+='<span class="displaypageNum"><a href="#" onclick="redirectpage('+jj+');return false">'+jj+'</a></span>'}else{html+='<span class="displaypageNum"><a href="#" onclick="redirectlabel('+jj+');return false">'+jj+'</a></span>'}}}
if(pageEnd<lastPageNo-1){html+='...'}
if(pageEnd<lastPageNo){if(currentPage=="page"){html+='<span class="displaypageNum"><a href="#" onclick="redirectpage('+lastPageNo+');return false">'+lastPageNo+'</a></span>'}else{html+='<span class="displaypageNum"><a href="#" onclick="redirectlabel('+lastPageNo+');return false">'+lastPageNo+'</a></span>'}}
var nextnumber=parseInt(currentPageNo)+1;if(currentPageNo<(lastPageNo-1)){if(currentPage=="page"){html+='<span class="displaypageNum"><a href="#" onclick="redirectpage('+nextnumber+');return false">'+nextText+'</a></span>'}else{html+='<span class="displaypageNum"><a href="#" onclick="redirectlabel('+nextnumber+');return false">'+nextText+'</a></span>'}}
if(currentPageNo<lastPageNo){if(currentPage=="page"){html+='<span class="displaypageNum lastpage"><a href="#" onclick="redirectpage('+lastPageNo+');return false">'+lastText+'</a></span>'}else{html+='<span class="displaypageNum lastpage"><a href="#" onclick="redirectlabel('+lastPageNo+');return false">'+lastText+'</a></span>'}}
var pageArea=document.getElementsByName("pageArea");var blogPager=document.getElementById("blog-pager");for(var p=0;p<pageArea.length;p++){pageArea[p].innerHTML=html}
if(pageArea&&pageArea.length>0){html=''}
if(blogPager){blogPager.innerHTML=html}}
function totalcountdata(root){var feed=root.feed;var totaldata=parseInt(feed.openSearch$totalResults.$t,10);looppagecurrentg(totaldata)}
function pagecurrentg(){var thisUrl=urlactivepage;if(thisUrl.indexOf("/search/label/")!=-1){if(thisUrl.indexOf("?updated-max")!=-1){postLabel=thisUrl.substring(thisUrl.indexOf("/search/label/")+14,thisUrl.indexOf("?updated-max"))}else{postLabel=thisUrl.substring(thisUrl.indexOf("/search/label/")+14,thisUrl.indexOf("?&max"))}}
if(thisUrl.indexOf("?q=")==-1&&thisUrl.indexOf(".html")==-1){if(thisUrl.indexOf("/search/label/")==-1){currentPage="page";if(urlactivepage.indexOf("#PageNo=")!=-1){currentPageNo=urlactivepage.substring(urlactivepage.indexOf("#PageNo=")+8,urlactivepage.length)}else{currentPageNo=1}
document.write("<script src=\""+home_page+"feeds/posts/summary?max-results=1&alt=json-in-script&callback=totalcountdata\"><\/script>")}else{currentPage="label";if(thisUrl.indexOf("&max-results=")==-1){perPage=20}
if(urlactivepage.indexOf("#PageNo=")!=-1){currentPageNo=urlactivepage.substring(urlactivepage.indexOf("#PageNo=")+8,urlactivepage.length)}else{currentPageNo=1}
document.write('<script src="'+home_page+'feeds/posts/summary/-/'+postLabel+'?alt=json-in-script&callback=totalcountdata&max-results=1" ><\/script>')}}}
function redirectpage(numberpage){jsonstart=(numberpage-1)*perPage;noPage=numberpage;var nameBody=document.getElementsByTagName('head')[0];var newInclude=document.createElement('script');newInclude.type='text/javascript';newInclude.setAttribute("src",home_page+"feeds/posts/summary?start-index="+jsonstart+"&max-results=1&alt=json-in-script&callback=finddatepost");nameBody.appendChild(newInclude)}
function redirectlabel(numberpage){jsonstart=(numberpage-1)*perPage;noPage=numberpage;var nameBody=document.getElementsByTagName('head')[0];var newInclude=document.createElement('script');newInclude.type='text/javascript';newInclude.setAttribute("src",home_page+"feeds/posts/summary/-/"+postLabel+"?start-index="+jsonstart+"&max-results=1&alt=json-in-script&callback=finddatepost");nameBody.appendChild(newInclude)}
function finddatepost(root){post=root.feed.entry[0];var timestamp1=post.published.$t.substring(0,19)+post.published.$t.substring(23,29);var timestamp=encodeURIComponent(timestamp1);if(currentPage=="page"){var pAddress="/search?updated-max="+timestamp+"&max-results="+perPage+"#PageNo="+noPage}else{var pAddress="/search/label/"+postLabel+"?updated-max="+timestamp+"&max-results="+perPage+"#PageNo="+noPage}
location.href=pAddress}
/*]]>*/
</script>
</b:if>
</b:if>
```
ラベルページにも適用するには、テーマ -> HTML の編集 で次のコードスニペットを探して
```html
expr:href='data:label.url'
```
次のように perPage の値に合わせるようにする（特殊文字は実体参照で入力する）
```
expr:href='data:label.url + "?&max-results=13"'
```
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