Page Navigation

navigate_sections.js

var chaperRegex = /(chapter)(\d{1,2})(-)(\d{1,2})/

function LoadNextSection() {
	// build next section address
    var nextSectionUrl = window.location.href.replace(chaperRegex, 
        function(match, first, chapter, second, section) {
            var nextSection = +section+1 						   // increment
            if (nextSection < 10) nextSection = "0" + nextSection; // pad with 0
            return first + chapter + second + nextSection;
        });

	// make sure page exists by fetching first
	$.get(nextSectionUrl,function(data) {
		var notFound = data.startsWith("<script")
        if (notFound) {
			LoadNextChapter();
        } else {
			ReplacePage(data, nextSectionUrl)
        }

    })
}

function LoadPrevSection() {
	// build next section address
    var prevSectionUrl = window.location.href.replace(chaperRegex, 
        function(match, first, chapter, second, section) {
            var nextSection = +section-1 						   // increment
            if (nextSection < 10) nextSection = "0" + nextSection; // pad with 0
            return first + chapter + second + nextSection;
        });

	// make sure page exists by fetching first
	$.get(prevSectionUrl, function(data) {
		var notFound = data.startsWith("<script")
        if (notFound) {
			LoadNextChapter();
        } else {
			ReplacePage(data, prevSectionUrl)
        }

    })
}

function ReplacePage(data,url) {
	// two approaches: either full page re-load, or replace contents and push history
    //window.location = url;
    var htmlDoc = (new DOMParser()).parseFromString(data, "text/xml");
    var $content = $(htmlDoc).find("body .container")
    $(".container").html($content.html())
    history.pushState({},"next page",url)
}

$("body").on("keyup",function(e) {
	if (e.keyCode === 39) {
		// go right
		LoadNextSection()
    } else if (e.keyCode === 37) {
		// go left
		LoadPrevSection()
    }
	// else who cares
  })
  .css("display","block"); // make sure page is visible