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How to check what are adjacent characters?

I'm creating a markdown editor and I need to check if neighbor characters are specific characters, then remove them, else append them.
For e.g I want to check selected-text, tow neighbor characters are **, then remove them, else append them around selected text.
I can get selected text using this approach:
function getSelection(elem) {
var selectedText;
if (document.selection != undefined) { // IE
elem.focus();
var sel = document.selection.createRange();
selectedText = sel.text;
} else if (elem.selectionStart != undefined) { // Firefox
var startPos = elem.selectionStart;
var endPos = elem.selectionEnd;
selectedText = elem.value.substring(startPos, endPos)
}
return selectedText;
}
$(document).on('mousedown', 'button', function(e) {
var selection = getSelection( $('#txtarea').get(0) );
alert(selection);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea id="txtarea">this is a test</textarea>
<button>Bold (toggle)</button>
Now I need when user clicks on that button, it checks if selected text is between ** like this **selectedtext**, then remove them like this selected text else append them like this **selectedtext**. How can I do that?

Before anything I would like to refer to all the markdown editors out there: https://www.google.de/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=javascript%20markdown%20library
So: do not try to reinvent the the wheel, and so on.
But for the sake of learning, my approach would look like this:
function toggleMarker(marker, el) {
var markerLength = marker.length;
var startPos, endPos, selection, range;
if (document.selection != undefined) { // IE
el.focus();
range = document.selection.createRange();
selection = range.text;
} else if (el.selectionStart != undefined) { // Firefox
startPos = el.selectionStart;
endPos = el.selectionEnd;
selection = el.value.substring(startPos, endPos);
}
if (!selection.length){
return;
}
if (el.value.substring(startPos-markerLength,startPos) === marker
&& el.value.substring(endPos,endPos+markerLength) === marker
){
el.value = el.value.substring(0,startPos-markerLength) +
selection +
el.value.substring(endPos+markerLength);
}
else{
el.value = el.value.substring(0,startPos) + marker +
selection + marker + el.value.substring(endPos);
}
}
$(document).on('mousedown', 'button', function(e) {
toggleMarker( $(this).data('marker'), $('#txtarea').get(0) ).text;
});
See it in action: https://jsfiddle.net/t4ro53v8/4/
The solution takes a very generic approach: the marker to toggle is set as a custom data attribute to make it easy to reuse the code.
The functionality is only implemented for the non-IE case. You will have to check, how to determine startPos and endPos for a range in IE.
In all other browsers:
the selection is identified
nothing is done if nothing is selected
sourroundings of the selection are checked against the given marker
if both markers are present, they get deleted
otherwise the markers are inserted
As a proof of concept this example works like a charm.
But there are some shortcomings:
How to distinguish between bold text(**) and italics(*)?
How to handle markers that just appear just on one side of the selection
What to do, if a marker is selected?
But that is for you to solve now ...

You could use regex to find the occurance of a ** ** pattern.This regex will help you find the pattern similar to what you have.
[*][*][a-z]*[*][*] .
Using the exec() method, will help you extract that particular text.
Check the length of this using .length, if it is 4, then there is nothing in between, and you can replace it with the new text surrounded by **,
"**"+ newtext+"**"
For removing the **, you can use the replace() method, where you replace ** with whitespace or so.

How to implement break lines and paragraphs on contenteditable?

I’m building a simple text editor for Safari only. I need to implement a very specific behavior:
First enter - Creates <br> tag
Second enter (after <br>) - Create new paragraph
I’m already listening for enter on keypress event and using formatBlock to format paragraphs. How can I check if element before caret is a <br> element, so I can use formatBlock?
By default, Safari adds <div><br></div> on enter keypress, so I need to use preventDefault for first enter too. (code above)
I create new paragraphs using:
$("#content").live("keypress", function(e){
if (e.which == 13) {
document.execCommand("formatBlock", false, "p");
}
});
I can add br's using: ( Make a <br> instead of <div></div> by pressing Enter on a contenteditable )
if (window.getSelection) {
var selection = window.getSelection(),
range = selection.getRangeAt(0),
br = document.createElement("br");
range.deleteContents();
range.insertNode(br);
range.setStartAfter(br);
range.setEndAfter(br);
range.collapse(false);
selection.removeAllRanges();
selection.addRange(range);
return false;
}
UPDATE: User is typing a paragraph like this: <p>This is my paragraph</p>. At enter keypress, code should be <p>This is my paragraph<br></p> (cursor after br). Pressing enter for second time should result on <p>This is my paragraph</p><p></p> (cursor on second paragraph)

You could use keydown, for example:
<div id="textarea"></div>
Then in your script file:
document.getElementById("textarea").addEventListener("keydown",function(e){if(e.keyCode == 32) {ocument.getElementById("textarea").innerHTML+="<br />"} })
And your other stuff

DISCLAIMER: This is tested only on Chromium.
var sel = window.getSelection();
var range = sel.getRangeAt(0);
if ((sel.extentNode.previousElementSibling instanceof HTMLBRElement)
&& range.startOffset == 0)
{
// Do your magic to start a paragraph.
} else {
// Your existing code to add a <br> element since there is no <br> before it.
}

Determine when caret reaches the end of input box

I have found this question which provides a solution to compute the exact position of the caret in a text or input box.
For my purposes, this is overkill. I only want to know when the caret is at the end of all the text of an input box. Is there an easy way to do that?

In all modern browsers:
//input refers to the text box
if(input.value.length == input.selectionEnd){
//Caret at end.
}
The selectionEnd property of an input element equals the highest selection index.

<script>
input = document.getElementById('yourinputfieldsid');
if(input.selectionEnd == input.selectionStart && input.value.length == input.selectionEnd){
//your stuff
}
</script>
This checks to see if the caret actually is at the end, and makes sure that it isn't only because of the selection that it shows an end value.

You don't specify what you want to happen when some text is selected, so in that case my code just checks whether the end of the selection is at the end of the input.
Here's a cross-browser function that wil work in IE < 9 (which other answers will not: IE only got selectionStart and selectionEnd in version 9).
Live demo: http://jsfiddle.net/vkCpH/1/
Code:
function isCaretAtTheEnd(el) {
var valueLength = el.value.length;
if (typeof el.selectionEnd == "number") {
// Modern browsers
return el.selectionEnd == valueLength;
} else if (document.selection) {
// IE < 9
var selRange = document.selection.createRange();
if (selRange && selRange.parentElement() == el) {
// Create a working TextRange that lives only in the input
var range = el.createTextRange();
range.moveToBookmark(selRange.getBookmark());
return range.moveEnd("character", valueLength) == 0;
}
}
return false;
}

Selecting Part of String inside an Input Box with jQuery

I am trying to figure out how to highlight just some part of text inside an input box using jQuery. It's quite simple to highlight the entire contents of the input box but how do you highlight just one word or couple of letters?
Thanks!

For text <input> elements, the following will do the job. The example selects just the word "two" in the input:
function setInputSelection(input, startPos, endPos) {
input.focus();
if (typeof input.selectionStart != "undefined") {
input.selectionStart = startPos;
input.selectionEnd = endPos;
} else if (document.selection && document.selection.createRange) {
// IE branch
input.select();
var range = document.selection.createRange();
range.collapse(true);
range.moveEnd("character", endPos);
range.moveStart("character", startPos);
range.select();
}
}
document.getElementById("setSelection").onmousedown = function() {
var input = document.getElementById("i");
setInputSelection(input, 4, 7);
return false;
};
<input id="i" type="text" value="One two three">
<input type="button" value="Set selection" id="setSelection">

You will need to select the entire value, and then manipulate the string in code. Depending on what you're trying to do with the words, you might look in to using regular expressions to match certain words/letters.

Contenteditable text editor and cursor position

How can I (using jquery or other) insert html at the cursor/caret position of my contenteditable div:
<div contenteditable="true">Hello world</div>
For example, if the cursor/caret was between "hello" and "world" and the user then clicked a button, eg "insert image", then using javascript, something like <img src=etc etc> would be inserted between "hello" and "world". I hope I've made this clear =S
Example code would be greatly appreciated, thanks a lot!

The following function will insert a DOM node (element or text node) at the cursor position in all the mainstream desktop browsers:
function insertNodeAtCursor(node) {
var sel, range, html;
if (window.getSelection) {
sel = window.getSelection();
if (sel.getRangeAt && sel.rangeCount) {
sel.getRangeAt(0).insertNode(node);
}
} else if (document.selection && document.selection.createRange) {
range = document.selection.createRange();
html = (node.nodeType == 3) ? node.data : node.outerHTML;
range.pasteHTML(html);
}
}
If you would rather insert an HTML string:
function insertHtmlAtCursor(html) {
var sel, range, node;
if (window.getSelection) {
sel = window.getSelection();
if (sel.getRangeAt && sel.rangeCount) {
range = window.getSelection().getRangeAt(0);
node = range.createContextualFragment(html);
range.insertNode(node);
}
} else if (document.selection && document.selection.createRange) {
document.selection.createRange().pasteHTML(html);
}
}
I've adapted this from my answer to a similar question: How to find cursor position in a contenteditable DIV?

With contenteditable you should use execCommand.
Try document.execCommand('insertImage', false, 'image.jpg') or document.execCommand('insertHTML', false, '<img src="image.jpg" alt="" />'). The second doesn't work in older IE.

in this code i have just replace html code with (") to (')
use this syntax:
$("div.second").html("your html code and replace with (")to(') ");

I would recommend the use of the jquery plugin a-tools
This plugin has seven functions:
* getSelection – return start, end position, length of the selected text and the selected text. return start=end=caret position if text is not selected;
* replaceSelection – replace selected text with a given string;
* setSelection – select text in a given range (startPosition and endPosition);
* countCharacters – count amount of all characters;
* insertAtCaretPos – insert text at current caret position;
* setCaretPos – set cursor at caret position (1 = beginning, -1 = end);
* setMaxLength – set maximum length of input field. Also provides callback function if limit is reached. Note: The function has to have a number as input. Positive value for setting of limit and negative number for removing of limit.
The one that you need is insertAtCaretPos:
$("#textarea").insertAtCaretPos("<img src=etc etc>");
There might be a draw-back: this plugins only works with textarea en input:text elements, so there may be conflicts with contenteditable.