Develop Reference

How to cut string after a specific line number?

I have a string - project description ( as part of an object ) coming from a user form submission that is shown on a page of a report. If the line numbers exceed 24 I want to show the rest of the string on a new page. My initial idea was to cut it based on characters but this can't be done precisely as if line breaks are made when submitting the form, the characters can't be calculated as we don´t know if the line break was made in the middle of a line or the end or wherever. I don't know what could be the solution?
How can I cut a string based on number of lines?
This is what I have done so far:
function countLines (el) {
let projectDetails = $rootScope.report.description;
var el = document.getElementById(el);
var divHeight = el.offsetHeight
var lines = divHeight / 17;
//console.log("Lines counted: " + lines);
if(lines > 24) {
$scope.secondDescriptionPage = true;
$scope.projectDetailsTextFirstPart = // this should be calculated
//$scope.projectDetailsTextSecondPart = // this should be calculated )
}
}

With the -webkit-line-clamp CSS property you can cut text by a certain number of lines. See MDN for details. It will not work in IE11 however.

Javascript prepend to line in textarea on double click

What I am trying to do:
Double click a line in a textarea.
Prevent text from being selected.
Prepend a dash to that line.
I know some basic jquery but can't seem to understand the lower level javascript that is required. Here is what I have so far:
$("textarea").dblclick(function() {
//TODO: Prevent selection
//TODO: Get the line number??
//TODO: prepend a dash to the line
// or replace the line with itself
// plus the dash at the front??
});
Here is the fiddle.

There may be a number of things you need to do, but something like this should be enough to get you started:
$("textarea").dblclick(function() {
//first, get the position of the cursor
var cursorPosition = $(this).prop("selectionStart");
//get the text value at the cursor position
var textValue = $(this).val().substr(cursorPosition,1);
//use a loop to look backward until we find the first newline character \n
while(textValue != '\n' && cursorPosition >= 0) {
cursorPosition--;
textValue = $(this).val().substr(cursorPosition,1);
}
//update the textarea, combining everything before the current position, a dash, and everything after the current position.
$(this).val(($(this).val().substr(0,cursorPosition+1) + '-' + $(this).val().substr(cursorPosition+1)))
});
You can see an example in this JS Fiddle:
http://jsfiddle.net/igor_9000/4zk5otvm/2/
There will probably be a lot more you need to add to this, depending on what you want to be able to do with the function and what limits you want to enforce, but that should be enough to get you started. Hope that helps!

I needed something similar, here's what you might've been looking for with vanilla JS (without jQuery or anything):
function dblClickEvt(obj) {
let pos = obj.selectionStart;
let text = obj.value;
let lineStart = text.lastIndexOf("\n", pos);
let lineEnd = text.indexOf("\n", pos);
let before = ( lineStart === -1 ? '' : text.slice(0, lineStart + 1) ); // row(s) before incl. line break
let after = '';
if(lineEnd === -1) // -> last row is selected
lineEnd = undefined; // because -1 would cause the selection to strip the last character
else
after = text.slice(lineEnd); // row(s) after the selection
let selected = text.slice(lineStart + 1, lineEnd); // the selected row
// write new value (manipulate before, selection a/o after if you want)
obj.value = before + '-' + selected + after;
// reset cursor position:
obj.selectionStart = pos;
obj.selectionEnd = pos;
}
Use the "ondblclick" attribute of your textarea to call the function:
<textarea ondblclick="dblClickEvt(this)"></textarea>

This only supports modern browsers, if you want to support older browsers, then you need to get the method that calculates selectionStart. This is not fully tested and if you double click on a line that is selected, it toggles the dash. And when you set the new value, the selection goes away.
$("textarea").on("dblclick", function (evt) {
var taValue = this.value;
//if there is no text than there is nothing to do
if(!taValue.length) return;
//get the position of the selection (not supported old browsers)
var se = this.selectionStart;
//find where the previous line break is located (array lastIndexOf not supported old browsers)
//thinking about it, probably do not need to split... :)
var loc = taValue.substr(0, se).split("").lastIndexOf("\n")+1;
//separate the text by characters
var parts = taValue.split("");
//if the character is a -, than remove it
if (parts[loc]==="-") {
parts.splice(loc, 1);
} else { //else inject the -
parts.splice(loc, 0, "-");
}
//join the array back up into a string and set the value
this.value = parts.join("");
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea rows=10 cols=30>FOO FOO FOO
BAR BAR BAR
CAKE CAKE CAKE
WORLD WORLD WORLD</textarea>

to apply sequential line numbering to lines in a paragraph: is it possible?

Is it possible to have jquery/javascript insert sequential line number at the start of all lines in a paragraph and, better still, to follow the sequence through to subsequent paragraphs?
I want to be able to refer students quickly to particular lines of an article (in a classroom setting). I have lots of articles to which I would like to apply this functionality, each of which has varying numbers of paragraphs.
I was hoping this might be possible, even in a responsive page, where the width of the paragraphs changes, depending on the display device, and the consequent number of lines in each paragraph becomes greater or fewer.
Thanks in advance to anyone who can help.

Here is one approach that may suit your purposes.
Get the height of a one-line paragraph, for reference.
For each paragraph, get the actual height, and infer the number of lines.
Loop through the lines and add the numbering at absolute positions.
var refHeight = $("p").eq(0).height();
$("p").eq(0).remove();
var cnt = 1;
$("p").each(function(index) {
var pos = $(this).position();
var h = $(this).height();
var lines = h / refHeight;
var lineHeight = h / lines;
for (var i=pos.top ; i<pos.top+h ; i += lineHeight) {
var num = $("<p>", { class: "number" });
num.text(cnt++);
num.css("top", i);
$(this).before(num);
console.log(i);
}
});
(Fiddle)
Edit
If you wanted to use a fixed line length (so that everyone is seeing the same numbers), you could combine the above with the following:
Break the paragraphs into lines.
Wrap each line in a span/div, and re-append.
Block the browser from text wrapping.
$("p").each(function() {
var text = $(this).text();
$(this).html("");
var i=0;
while (i<text.length) {
lineCharWidth = charWidth;
while (i+lineCharWidth < text.length && text[i+lineCharWidth] != ' ') {
lineCharWidth++;
}
var line = $("<span>", { class: "line" }).text(text.substr(i, lineCharWidth));
$(this).append(line).append("<br/>");
i += lineCharWidth;
}
});
(Fiddle)

Here's a solution that uses a function to split the paragraph text on space characters based on a pre-determined line length and then replaces the text with an <ol> comprised of <li> elements each containing one line of text:
var lineNum = 1;
function splitLines(text, lineLen) {
var words = text.split(/\s/g), line = '', lines = [];
$.each(words, function(idx) {
line += this + ' ';
if (line.length > lineLen || idx == words.length - 1) {
lines.push(line);
line = '';
lineNum += 1;
}
});
return lines;
}
$('p').each(function() {
var $p = $(this), $ol = $('<ol start="' + lineNum + '">'), lineLen = 50;
$.each(splitLines($p.text(), lineLen), function(idx) {
$ol.append('<li>' + this + '</li>');
});
$p.text('').append($ol);
});
I'm not sure about the support for the start attribute of the <ol>. It does work in Chrome. Even still, I like using the list element because it's a little more semantically meaningful, in my opinion.

Sure. Just make sure you're encoding your line returns and use it to split up the text with a simple replace.
Sample text:
The quick
brown fox
jumped over
the lazy dog
for this, the actual string would be the following:
The quick\r\nbrown fox\r\njumped over\r\nthe lazy dog
I think something like this would work (without the document.write, and there could be performance improvements):
var input = '\r\nThe quick\r\nbrown fox\r\njumped over\r\nthe lazy dog';
input = input.replace(/\r\n/g, '<div class=\'index\'></div>');
document.write(input);
var idx = 0;
$('.index').each(function(){
$(this).text(idx++);
});
If I'm not mistaken, this should write out an index number on each line. Could use some testing/debugging, though :)
For an example of how this is done, check out Github's diff pages.

JavaScript - Reposition a DIV incrementally onClick

Very simple code, very simple problem. When a link is pressed, it moves a div either up or down. However, I cannot get it to move incrementally. I know this is a simple syntax error, but google isn't revealing the error of my ways. Anyone willing to enlighten me?
<a class="galsel" onclick="document.getElementById('innerscroll').style.bottom -='167px';">«</a>
<a class="galsel" onclick="document.getElementById('innerscroll').style.bottom +='167px';">»</a>
I already have it so that the div tiles itself vertically, so I'm not worried about it going "too high" or "too low"
Here's what it looks like right now: drainteractive.com/FBD/projects.php

You have to parse the value from the string containing px
// Increase by 167
document.getElementById('innerscroll').style.bottom = (parseInt(document.getElementById('innerscroll').style.bottom, 10) + 167) + ' px'
// Decrease by 167
document.getElementById('innerscroll').style.bottom = (parseInt(document.getElementById('innerscroll').style.bottom, 10) - 167) + ' px'
// Abstracted
function addToBottom(el, amount) {
// You probably add lower and upper bound check conditions
el.style.bottom = (parseInt(el.style.bottom) + amount) + ' px';
}
var el = document.getElementById('innerscroll');
addToBottom(el, 167);
addToBottom(el, -167);
Also be sure to make it work for cases where bottom wasn't set initially
var currentBottom = parseInt(document.getElementById('innerscroll').style.bottom) || 0;

+='167px' will concatinate it an it will become '167px167px167px167px167px'. Not sure what will result -='167px', but probably will result an error.

You need to rip the 'px' off the string, convert(?) it to an int, then subtract from that.
onclick="var mElem = document.getElementById('innerScroll'); mCur = parseInt(mElem.style.bottom.replace('px', 0)); mElem.style.bottom = (mCur-167)+'px'"
Naturally, this should all be put into a separate function, who is then called in the onclick, rather than the monstrosity above.
function moveUp()
{
var mElem = document.getElementById('innerScroll');
var mCur = parseInt(mElem.style.bottom.replace('px', 0));
mElem.style.bottom = (mCur-167)+'px';
}
...
<strike>onlick="moveUp()"</strike>
onclick="moveUp()"
My mind must have been somewhere else..

Fast JS Pagination for long texts

I'm trying to create a pagination system with JavaScript.
Basic situation: I have a database, which holds fairly long texts (story chapters, 5000 words+). I want to display these chapters on a website...however not the entire text at once, because that would pretty much kill the readability, but in pages.
I have no problem displaying the text, but rather with getting the pages right.
I've been looking around, and came across a JQuery code, which does about what I want it to do...however there's a major caveat for this method. It takes about 10 seconds to finish paginating the text, which is far too long a wait.
What the code basically does:
It splits the text into words (separated by spaces).
It then tries adding one word after the other to a innerHTML, checking back if the text is now bigger than the container it's supposed to fit in.
Each time it breaks the boundary, it reverts back to the previous string and creates a new page. (By encapsulating the text into a span, which can then be hidden/shown at a moments notice) This works, however it is too slow, because it has to run these checks 5000+ times.
I have tried creating an approximation system, which basically takes the amount of words, divides it by the factor 0.5, checks if the buffer is larger than the required size, and repeats this process, until the buffer is 'smaller' than the required size for the first time, and from that position on, it fills the buffer, until it's full.
However it just doesn't seem to work right (double words, lines, which aren't completely full, and it's still too slow.)
This is the code I'm currently using, I'd be grateful for any fixes and suggestions how to make it easier, and especially: Faster.
Oh and: No, paging it serverside is not an option, since it's supposed to fit into variable browser formats...in a fullscreen browser at 1280x768 resolution it will be less pages, than in a small browser at a 1024x768 resolution.
function CreateChild(contentBox, Len, pageText, words) {
var Child = document.createElement("span");
Child.innerHTML = pageText;
contentBox.appendChild(Child);
if(Len == 0) ++Len;
words.splice(0, Len);
return words.length;
}
$(document).ready(function(){
var src = document.getElementById('Source');
var contentBox = document.getElementById('content');
var inner = document.getElementById('inner');
//get the text as an array of word-like things
var words = src.innerHTML.replace(/ +/g, " ").split(' '), wCount = words.length;
//start off with no page text
var pageText = null, cHeight = contentBox.offsetHeight;
while(words.length > 0) {
var Found = false;
pageText = words[0]; //Prevents constant checking for empty
wCount *= 0.5; //Searches, until the words fit in.
for(var i = 1; i < wCount; ++i) pageText += ' ' + words[i];
inner.innerHTML = pageText;
Distance = inner.offsetHeight - cHeight;
if(Distance < 40) { //Less than two lines
wCount = Math.floor(wCount);
if(Distance < 0) { //Already shorter than required. Fill.
for(var i = wCount; i < words.length; ++i) {
//add the next word to the pageText
var betterPageText = pageText + ' ' + words[i];
inner.innerHTML = betterPageText;
//Checks, whether the new words makes the buffer too big.
if(inner.offsetHeight > cHeight) {
wCount = CreateChild(contentBox, i, pageText, words);
Found = true;
break;
} else {
//this longer text still fits
pageText = betterPageText;
}
}
} else {
for(var i = wCount; i >= 0; --i) {
//Removes the last word from the text
var betterPageText = pageText.slice(0, pageText.length - words[i].length - 1);
inner.innerHTML = betterPageText;
//Is the text now short enough?
if(inner.offsetHeight <= cHeight) {
wCount = CreateChild(contentBox, i, pageText, words);
Found = true;
break;
} else {
pageText = betterPageText;
}
}
}
if(!Found) CreateChild(contentBox, i, pageText, words);
}
}
//Creates the final block with the remaining text.
Child = document.createElement("span");
Child.innerHTML = pageText;
contentBox.appendChild(Child);
//Removes the source and the temporary buffer, only the result remains.
contentBox.removeChild(inner);
src.parentNode.removeChild(src);
//The rest is the actual pagination code, but not the issue
});

I managed to solve my problem, also thanks to Rich's suggestion.
What I'm doing: First off, I'm getting the text from the 'Source' (alternatively, I could write the entire text straight into the JS, the effect is the same).
Next I'm getting references to my target any my temporary buffer, the temporary buffer is located inside the target buffer, so it will retain the width information.
After that, I split the entire text into words (standard RegEx, after replacing multiple spaces with a single one). After this, I create some variables, which are meant to buffer function results, so the function calls won't have to be repeated unnecessarily.
Now the main difference: I take chunks of 20 words, checking whether the current chunk exceeds the boundary (again, buffering the results in variables, so they don't get called multiple times, function calls equal valuable microseconds).
Once the boundary is crossed (or the total number of characters is reached), the loop is stopped, and (assuming the boundary caused the 'stop'), the text is shortened by one word per run, until the text fits in again.
Finally, the new text gets added to a new span-element, which is added to the content box (but made invisible, I'll explain why in a bit), the words I just 'used' get removed from the word array and the wCount variable gets decremented by the number of words.
Rinse and repeat, until all pages are rendered.
You can exchange the '20' with any other value, the script will work with any arbitrary number, however please remember, that a too low number will cause a lot of runs in the 'adding segment', and a too big number will cause a lot of runs in the 'backtracking segment'.
As for the invisible: If the span is left visible, sooner or later it WILL cause scrollbars to appear, effectively narrowing the width of the browser window.
In turn, this will allow less words to fit in, and all following pages will be distorted (because they will be matched to the window with scrollbars, while the 'paged result' will not have scrollbars).
Below is the code I used, I hope it will help someone in the future.
var src = document.getElementById('Source');
var contentBox = document.getElementById('content');
var inner = document.getElementById('inner');
//get the text as an array of word-like things
var words = src.innerHTML.replace(/ +/g, " ").split(' ');
//start off with no page text
var cHeight = contentBox.offsetHeight, wCount = words.length;
while(wCount > 0) {
var Len = 1, Overflow = false;
var pageText = words[0]; //Prevents the continued check on 'is pageText set'.
while(!Overflow && Len < wCount) { //Adds to the text, until the boundary is breached.
//20 words per run, but never more than the total amount of words.
for(var j = 0; j < 20 && Len < wCount; ++Len, ++j) pageText += ' ' + words[Len];
inner.innerHTML = pageText;
Overflow = (inner.offsetHeight > cHeight); //Determines, whether the boundary has been crossed.
}
if(Overflow) { //Will only be executed, if the boundary has been broken.
for(--Len; Len >= 0; --Len) { //Removes the last word of the text, until it fits again.
var pageText = pageText.slice(0, -(words[Len].length + 1)); //Shortens the text in question.
inner.innerHTML = pageText;
//Checks, whether the text still is too long.
if(inner.offsetHeight <= cHeight) break;//Breaks the loop
}
}
var Child = document.createElement("span");
Child.style.display = "none"; //Prevents the sidebars from showing (and distorting the following pages)
Child.innerHTML = pageText;
contentBox.appendChild(Child);
words.splice(0, Len);
wCount -= Len;
}

Create an absolutely-positioned container that is the width of a single page. Give it height of 'auto'. Position the container somewhere off screen, like left: -10000px so users can't see it. Split the original text into 20-word chunks. (Look up the regex that accomplishes this.) Append one chunk at a time to the string in the container until the height of the container reaches the max height of a single page. Once it reaches the max height, the string in the container is basically one page of text. Push the string in the container onto an array called 'pages'. Empty the container and start creating page 2 by appending the 20-word chunks again, continuing to iterate through the array from where you left off on the previous page. Continue this process until you reach the end of the 20-word array, pushing each new page onto the array of pages whenever the container's string reaches the max height. You should now have an array of pages, each item of which contains the text of each page.

Having not searched in advance, I worked out an alternative solution with getClientRects (https://developer.mozilla.org/en-US/docs/Web/API/Element/getClientRects). If someone's interested in the details, I'll post more.