Develop Reference

Display dynamic html content like an epub/ebook, without converting html to epub format?

I want to create a responsive, mobile optimized reading experience similar to an epub/ebook reader, like the Kindle app, or iBooks, using dynamic html as the source.
Imagine a long article or blog post that requires a lot of vertical scrolling to read, especially on a small mobile device. What I would like to do is break the long page into multiple full-screen sections, allowing the user to use left/right navigation arrows and/or the swipe gesture to "page" through the article.
There are many JS libraries available that can create a "slide show" or "carrousel" of pre-defined slides (using divs or other container elements). But I want the text and html content to dynamically re-flow to fit any device viewport and still be readable... just like an epub/ebook user interface, like the Kindle app or iBooks. So, for the same article, there would be many more "pages" on a phone than there would be on a tablet or desktop viewport, and those "pages" would need to be dynamically created/adjusted if/when the viewport size changes (like switching from portrait to landscape on a mobile device).
Here is an example of a javascript .epub reader: epub.js
... notice the responsive behavior. When you resize your viewport, all the text re-flows to fit the available space, increasing or decreasing the total number of "pages". The problem is that epub.js requires an .epub file as its source.
What I want is the same user interface and functionality for an html page.
I have searched and searched for some kind of library that can do this out of the box, but haven't been able to find anything.
I realize that I could use a conversion script to convert my html page into an .epub file, and then use epub.js to render that file within the browser, but that seems very round-about and clunky. It would be so much better to mimic or simulate the .epub reader user experience with html as the direct source, rendering/mimicking a client side responsive ebook user experience.
Does anyone know if something like this already exists, or how I could go about building it myself?
The crucial functionality is the dynamic/responsive text-reflow. When the viewport dimensions are reduced, the text/content needs to reflow to the next "page" to avoid any need for vertical scrolling. I don't know how to do this efficiently. If I were to code it myself, I might use something like the jQuery Columnize plugin, setting all columns to width: 100vw; height: 100vh, so that each column is like a "page", and then figuring out how to create a swipe UI between those "pages".
Any help is much appreciated!

This becomes very difficult if the html page is complex, eg with precisely positioned elements or images. However if (as in the epub.js example) the content consists only of headings and paragraphs, it is achievable.
The basic idea is to progressively add content until just before the page overflows. By keeping track of where we start and stop adding content, clicking to the next page is a case of changing the page start to the previous page end (or vice versa if you're going back).
Process for reshaping content into pages
Let's assume you have all your content in one long string. Begin by splitting all the content into an array of words and tags. It's not as easy as splitting by whitespace as whitespace between < and > should be ignored (you want to keep classnames etc within each tag). Also tags should be separated as well, even if there is no whitespace between the tag and a word.
Next you need a function that checks if an element's contents overflow the element. This question has a copy-paste solution.
You need two variables, pageStart and pageEnd, to keep track of what indexes in the array are the beginning and end of the current page.
Beginning at the index in pageStart you add elements from the array as content to the page, checking after each add whether or not the contents overflow. When they do overflow you take the index you're up to, minus 1, as the index for pageEnd.
Keeping tags across page breaks
Now if all's ticketyboo then this should fill the page pretty well. When you want to go to the next page set your new pageStart as pageEnd + 1 and repeat the process. However there are some issues that you may want to fix.
Firstly, what happens if the page overflows in the middle of a paragraph? Strictly speaking the closing tag, </p>, is not required in HTML, so we don't need to worry about it. But what about the start of the next page? It will be missing an opening tag and that is a major problem. So we have make sure we check if the page's content begins with a tag, and if it doesn't then we get the closest opening tag prior to the current pageStart (just step back along the array from pageStart) and add it in before the rest of the content.
Secondly, as shown in the example, if a paragraph continues onto the next page, the last line of the current page is still justified. You need to check if pageEnd is in the middle of a paragraph and if so add syle="text-align-last:justify;" to the opening tag of that paragraph.
Example implementation
A pen showing all this in action is at https://codepen.io/anon/pen/ZMJMZZ
The HTML page contains all content in one long element. The content is taken directly from the container #page and reformed into pages, depending on the size of #page. I have't implemented justifying the last line if a page break occurs within a paragraph. Resize the #page element in the css and see how the content resizes itself - note that since the page size is fixed you'll have to use click forward and back to trigger a recalculation. Once you bind the page size to the window size, recalculating pages on the fly simply involves adding a resize event listener to the window that calls fillPage.
No doubt there are numerous bugs, indeed it will sometimes display things incorrectly (eg skipping or repeating words at the beginning or end of a page), but this should give you an idea of where to start.

Take a look at this repository on GitHub. Otherwise, you can create a one-page website with many sections, each one as high as the viewport, by using only CSS (demo):
.section { height: 100vh; }
or by using JavaScript, adding an anchor to each section to navigate between them, and applying a responsive unit (my demo) for the text of each section, to adapt it on resize... Something like this:
var curr_el_index = 0;
var els_length = $(".container").length;
$(".next_section").on("click", function(e) {
curr_el_index++;
if (curr_el_index >= els_length) {
curr_el_index = 0;
}
$("html, body").animate({
scrollTop: $(".container").eq(curr_el_index).offset().top
}, 300);
return false;
});
$(".previous_section").on("click", function(e) {
curr_el_index--;
if (curr_el_index < 0) {
curr_el_index = els_length - 1;
}
$("html, body").animate({
scrollTop: $(".container").eq(curr_el_index).offset().top
}, 300);
return false;
});
* {
border: 0;
margin: 0;
padding: 0;
box-sizing: border-box;
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
}
body {
background-color: #1a1a1a;
}
section {
height: 100vh;
background-color: #eee;
border: 2px solid red;
font-size: 6vw;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<section class="container">Section 1 Previous Next</section>
<section class="container">Section 2 Previous Next</section>
<section class="container">Section 3 Previous Next</section>
<section class="container">Section 4 Previous Next</section>
<section class="container">Section 5 Previous Next</section>
EDIT #1
An idea of algorithm, that come from a my codepen, that uses the same jQuery plugin:
Create your reader layout, copying the whole text in it
Use this jQuery plugin to check the text inside the viewport (demo)
Count the number of characters/WORDS with "Onscreen" label in the
viewport (a references)
Split the whole text in a list containing as many characters/WORDS as
there are in the "Onscreen" label
Create a section for each element of the obtained list, filling each
section with the relative text; the number of elements of the list
gives you the number of pages (sections) of the whole text. You may
navigate between sections like above
On resize event, redo [2-5] algorithm steps
Cheers

The idea is to have a div that will contain the whole text (let's call this div #epub_container). Then, you will have a div with the same size of the page viewport (let's call it #displayer) and it will contain #epub_container.
#displayer will have css overflow:hidden. So when the site loads, it will only show the first page, because the rest of the #epub_container will be hidden.
Then you need a page navigator to increment/decrement the page number. When the page number changes, we will move the top offset of the #epub_container based on that.
This is the jQuery function:
function move_to_page() {
var height = window.innerHeight;
var width = window.innerWidth;
var $displayer = $('#displayer');
var offset = $displayer.offset();
$displayer.height(height - offset.top - 5);
var $epub = $('#epub_container');
var offset_top = offset.top - $displayer.height() * m_page;
$epub.offset({top: offset_top, left: offset.left});
}
JSFiddle
EDIT: call move_to_page() after the text reflow in order to recompute the pages.

I created a plugin that handles this perfectly. It has features like dark mode, font changing, line height adjustment, select chapter in a side nav menu, save and restore scrolling/reading position. You can find it for free on git hub at https://github.com/E-TechDev/Html-Book-Reader
Screenshots
Light Mode Dark Mode Side Nav Menu Change Font Adjust Paragraph

You can try CSS scroll snap points on text with columns
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Scroll_Snap_Points
Somehow make the columns as wide as the viewport, and allow horizontal snapped scrolling.
Update
I mean to try to do the text flowing entirely using css. Pen:
https://codepen.io/ericc3141/pen/RYZEpr
body {
scroll-snap-type: mandatory;
scroll-snap-points-x: repeat(100%);
}
#columns-test {
height: 80vh;
columns: 90vw auto;
}

All you need is to insert a page break at the right places when you load the page. You can take the cue from here:
Dynamic Page-Break - Jquery
Here you can set the page height to your viewport height. You can handle the rest with javascript and css.

Contenteditable divs hide content after reloading

For text editing purposes I use contenteditable divs in a website. When I edit some text the div height is growing dynamically and all other elements on the webiste below shift downwards. That's what I want. Finally I store the content via Ajax on a server. So far everything is working fine.
The problem is when I reload the content from the server the height of the contenteditable divs does not grow automatically to show all it's content. Instead its height stay in the initial size.
BTW, this is true for all browsers.
Does anyone have some hints to overcome this issue ?
EDIT
This is the html and javascript contendeditable relevant code
<div class="editable" contentEditable=true onkeyup="autoGrowSave(this)" onblur="update(this)" ></div>
function autoGrowSave (oField) {
if (oField.scrollHeight > oField.clientHeight) {
oField.style.height = oField.scrollHeight + "px";
}
}
I use above javascript function to auto grow the contenteditable. Actually I do not know if even I need it. The jsFiddle example from Abhitalks below does not need one. Hmm ... I have to try without...
To store content on a sever I use the onblur attribute, which works perfect.

I answer the question myself. Thanks to Abhitaks jsFiddle I found the problem which limited to auto adjust the height. For this I appreciate the answer of course ;-)
In a CSS declaration I gave the class editable an initial height of 20px. Because of this the contenteditable could not adjust its height automatically. In turn I needed the javascript function autoGrow() to compensate this issue. While this "crazy" approach worked when editing the content, it did not work when reloading the content.
So the solution is to eliminate the heightin the CSS declaration and get rid of the javascript function autoGrow(). Now it works perfect !

Javascript split text string to fit within div element pages

I have been using overflow scroll to display the text. I realize that the overflow property can detect when the data is larger than will fit.
I need to fill one div element, then another, and so on until all the data is set within pages. The breaks can't break a word.
Only one page/div will be display: block; and the rest will be display: none;
What is the best way to allow data to be displayed on multiple div pages?

Why not you use css for this purpose?
<div style="height:50px; width:50px; overflow:hidden">testing</div>

Ali is right in using CSS to address this, but you should use the CSS word-wrap property to easily acheive your desired effect with the overflow content, as Ali's example edited below.
<div style="height:auto; min-height:50px; width:50px; word-wrap:break-word;">testing<div>
The word-wrap property is now supported in all major browsers.
Also as shown above, if you want to be sure that all the text shows as well as wraps in the correct place, then change your height CSS to 'height:auto; min-height:50px;'. This will allow the div to expand in height to show any overflow that would normally be hidden just defining a fixed height, while retaining the preferred size of 50px if possible, and retaining the desired word wrap not breaking a word in the middle.
The only exception where this will not work, is if a word is so long as to be longer than the width of the containing div, in which case it will break the long word at the last character that will fit on the line before continuing the word on the next line.
It's got to be an awfully long word though to run into this. If you use auto for the width property as done in the example with the height, it will fix the word break problem by allowing the width of the div to change, although in page layout it is usually more important to constrain a width much more than a height.

How to have transparent fonts except for the 'text-caret' in a textarea?

I have a simple textarea and I need to make transparent letters while allowing the text-caret to be visible. When I apply the following rules then I get invisible caret:
textarea {
background: transparent;
opacity: 0;
}
When I type invisible text, I need to see the text-caret move.
EDIT: I need to make editor to edit td cell in table. When I click on a cell I show a textarea and start typing. On a each character letter, I insert a context in a cell. After that, I hide a textarea.

This jsFiddle DEMO uses an online tutorial method that has been slightly modified to create a non-native browser text-caret along with transparent text.
Also, this jsFiddle New Method I created handles that goal differently but isn't IE8 friendly.
Status Update: I've improved the above jsFiddle DEMO with this newer version titled:
jsFiddle New Method that's Newer!!
The above jsFiddle version now allows the inside of the text-area to be clicked and the caret will respect that clicked location. This extra functionality was made possible by a great question and answer here.

Time to throw my $0.02 in.
This is an answer to the question, as I understood it, that works, it's quick and dirty, so feel free to make suggestions. This code is untested, but I did create a working fiddle here: http://jsfiddle.net/66RXc/
<html>
<head>
<title>Testing</title>
<script type="text/javascript">
<!--
function call(val) {
document.getElementById('result').value += val.charAt(val.length - 1);
document.getElementById('result').value =
document.getElementById('result').value.substr(0, val.length);
document.getElementById('test').value =
document.getElementById('test').value.replace(/[^\^]/g, ' ');
}​
-->
</script>
</head>
<body>
<textarea name="textarea" cols="20" rows="5" id="test"
onKeyUp="call(this.value);"></textarea>
<textarea style="display:block" cols="20" rows="5" id="result" disabled>
</textarea>​
</body>
</html>
The way I approached it was every time a character is typed in textarea "test", copy it over to a hidden text box, and replace all the characters in "test" except ^ with spaces. The characters are hidden, and the carat is still there. The full text is still in the other box. You could use display:hidden instead of display:block to hide it.
This isn't exactly the best implementation in the world, just something I did quickly. You have to type kind of slow (~15-20 WPM) for it to work.

Here is a CSS3 solution for making the text, itself, transparent:
Set the color attribute to be color: rgba(0,0,0,0); for the text
The only problem is that the caret goes invisible to. I did a quick search and found out that the caret and its styling are completely at the disposal of the browser. As such, the only option that I can think of for you is to use Javascript to add a simulated caret to the end of what you are typing.
I have an idea of how to do this, but it's messy and I wouldn't exactly call it ideal - I am, however, going to write it in case it helps further someone else's idea:
add a hidden label to the page
make sure it's hidden and not display: none; (so that it has actual width)
set white-space: nowrap; to keep it all on one line)
make sure the text is styled exactly the same as the text in the textarea
add the element <span id="caret">|</span> right before the textarea (I will refer to this as the caret for the rest of the spec)
set its position to position: relative;
increase its z-index to make it overlay
shift it right in order to set it on top of where the ACTUAL caret's initial position would be
make a function to check take in the value of the textarea and check the width of the textarea against the position of the caret (lookup selectionStart if you don't know how to do this)
the problem here is that characters are not always the same length, nor are they always the same length as their counterparts in other fonts
to solve this, as text is entered into the textarea you should have it imitated in the hidden label you created in step 1
imitate only the text from the start of the textarea to the caret's current position
wrap each character (including spaces) in their own span
next you will have to call a function to compare the width of the label with the width of the textarea
if the label is less wide than the textarea, get the width of the last span in the hidden label and shift the caret to the right by that width, then move on to step 4
as this is function will be run as text is entered it will happen one character at a time
be careful here that the caret doesn't go outside the textarea when it's in its last and near last positions
if the label is wider than the textarea:
add the widths of the characters (spans) in the label one at a time until you reach the width of the textarea
shift the position of the caret down by the height of the font and back to the horizontal starting position (as the caret's position is relative, just change its left position back to (0 + offsetToACTUALCaretPosition)
use a flag (e.g. class="break") to mark the last span (character) in the previous row
call the width comparison function again
make sure that you include a condition to check for the flags that you added at the end of each "row" (if any)
if you haven't already, apply any desired CSS styles to the caret span and change the color of the textarea's text to be color: rgba(0,0,0,0);
Caveats:
this will have a lot of overhead for the tiny job it does
you will have to adjust this method to account for padding
you will have to adjust this method to add support for deleting characters and moving the carets to an earlier position (to the left)
if you leave the textarea scrollable, you will have to add support for that (also for similar settings, like static heights causing text to scroll or move off screen/out of the textarea's visible area)
As I said before, I know that this solution is very rough, but it may help someone come up with a better one.
Good luck!

Based on your edit, if you need to just hide a textarea why don't you use jQuery $('#your_id').hide();

How to distinguish between blank areas and non-blank areas in a webpage with JavaScript?

How to distinguish between blank areas and non-blank areas in a webpage with JavaScript? Blank areas including:
areas that are not occupied by DOM elements.
margins, borders and paddings of DOM elements.
EDIT:
As response to the first comment: I am working on a web-based ebook reader. Cursor is set to {cursor:move} for blank areas so that the user can drag and scroll the webpage.

You could recursively go through each element and attach onmouseover and onmouseout events (where the former enables the text cursor and the latter enables the move cursor) on each which has text in it, e.g:
function attachEvents(e) {
if (n.nodeType == 3) { // Node.TEXT_NODE
// A text node - add the parent as an element to select text in
e.parentNode.onmouseover = elmMouseOver /* define your own event fns */
e.parentNode.onmouseout = elmMouseOut
}
else if (n.nodeType == 1) { // Node.ELEMENT_NODE
for (var m=e.firstChild; m != null; m = m.nextSibling) {
attachEvents(m)
}
}
}
The best way I can think of to make sure it's actually "text" which is moused over and not a blank area is to use e.g. <div><span>content</span></div> and put the mouseover/mouseout events in the <span> so that blank areas don't trigger events. This is what I'd recommend doing if you can, as things can get very complicated if you use block elements with padding from my experience. For example:
| The quick brown fox jumps |
| over the lazy dog | <- onmouseover/out of SPANs will ignore the space
after "dog" while DIVs won't and you won't need
to calculate padding/margins/positions which
makes it faster and more simple to implement
If you have to use block DIVs: You could use something like jQuery's jSizes plugin to get margins/padding in pixels or this (for a way to get the inherited CSS values and parse yourself by removing the px part from the end etc)
After that, you could figure out the position using position() in jQuery. I personally don't use jQuery for my stuff, but I use those specific "find positions" functions and found them to be one of the best I think in large part because of number of users testing them.
Good luck!

My advice would be to go for a simple scrollbar. That's far more foolproof. By trying to implement the cool drag-and-scroll feature you risk with a lot of buggy behavior in dozens of edge-cases none of us can even imagine.
If you really want to detect clicks in whitespace, you could try attaching to the onmousedown/onmouseup/onmousemove events for the page itself. JavaScript events bubble nicely, so you'll handle the whole page at once (unless it has some JavaScript in itself, in which case you're screwed anyway). These events supply both the mouse X/Y coordinates and the element that was clicked. Then you can check for padding of that element (careful with inline elements) and figure out if it's in the padding or not. You do not need to check the margin because clicking there will instead originate the click in the parent element.
Although the effect you get this way is a lot of scattered "drag-zones" that the user will have to hunt for in order to scroll the page. I doubt this will sit well with your users. Better then make the whole page "draggable", but then you will loose the ability to select text. Or do like Acrobat, which only allows grabbing in the considerable padding area of the page itself (then you should make sure that there is a considerable padding area). Which in my eyes is not much better than a scrollbar. :P