Develop Reference

How do I replace string within quotes in javascript?

I have this in a javascript/jQuery string (This string is grabbed from an html ($('#shortcode')) elements value which could be changed if user clicks some buttons)
[csvtohtml_create include_rows="1-10"
debug_mode="no" source_type="visualizer_plugin" path="map"
source_files="bundeslander_staple.csv" include cols="1,2,4" exclude cols="3"]
In a textbox (named incl_sc) I have the value:
include cols="2,4"
I want to replace include_cols="1,2,4" from the above string with the value from the textbox.
so basically:
How do I replace include_cols values here? (include_cols="2,4" instead of include_cols="1,2,4") I'm great at many things but regex is not one of them. I guess regex is the thing to use here?
I'm trying this:
var s = $('#shortcode').html();
//I want to replace include cols="1,2,4" exclude cols="3"
//with include_cols="1,2" exclude_cols="3" for example
s.replace('/([include="])[^]*?\1/g', incl_sc.val() );
but I don't get any replacement at all (the string s is same string as $("#shortcode").html(). Obviously I'm doing something really dumb. Please help :-)

In short what you will need is
s.replace(/include cols="[^"]+"/g, incl_sc.val());
There were a couple problems with your code,
To use a regex with String.prototype.replace, you must pass a regex as the first argument, but you were actually passing a string.
This is a regex literal /regex/ while this isn't '/actually a string/'
In the text you supplied in your question include_cols is written as include cols (with a space)
And your regex was formed wrong. I recomend testing them in this website, where you can also learn more if you want.
The code above will replace the part include cols="1,2,3" by whatever is in the textarea, regardless of whats between the quotes (as long it doesn't contain another quote).

First of all I think you need to remove the quotes and fix a little bit the regex.
const r = /(include_cols=\")(.*)(\")/g;
s.replace(r, `$1${incl_sc.val()}$3`)
Basically, I group the first and last part in order to include them at the end of the replacement. You can also avoid create the first and last group and put it literally in the last argument of the replace function, like this:
const r = /include_cols=\"(.*)\"/g;
s.replace(r, `include_cols="${incl_sc.val()}"`)

JavasScript Regex to exclude specific characters which are stored in a string variable, spaces, and change remaining characters to underscores

This is for a hangman-type guessing game. I already figured out how to use a Regex to display the letters as underscores on the page with appropriate spacing. Now I want use a Regex to do the following, all in one expression:
Check a string containing the correct answer this.answers[arraysIndex], against the string containing all of the user's correct guesses rightString
In the correct answer string: change only the letters that don't match the correct guesses string into underscores. This means I want to keep the spaces unchanged too.
I've tried this:
var regex = new RegExp("/(?![^"+rightString+"])/[\A-Za-z/])/","g");
newDisplay = (this.answers[arraysIndex]).replace(regex, "_");
...and this:
newDisplay = (this.answers[arraysIndex]).replace("/(?![^+rightString+])/[\A-Za-z/])/g", "_")
...and countless slight variations of each. I'm not married to the idea of using a string variable, I could use an array variable too, or maybe there's something that hasn't even occurred to me. I've researched exhaustively on here and many other resources (that's how I solved my first problem) but this one's got me beat. Any help is greatly appreciated.

Matching a JS string with regex

I have a long xml raw message that is being stored in a string format. A sample is as below.
<tag1>val</tag><tag2>val</tag2><tagSomeNameXYZ/>
I'm looking to search this string and find out if it contains an empty html tag such as <tagSomeNameXYZ/>. This thing is, the value of SomeName can change depending on context. I've tried using Str.match(/tagSomeNameXYZ/g) and Str.match(/<tag.*.XYZ\/>/g) to find out if it contains exactly that string, but am able to get it return anything. I'm having trouble in writing a reg ex that matches something like <tag*XYZ/>, where * is going to be SomeName (which I'm not interested in)
Tl;dr : How do I filter out <tagSomeNameXYZ/> from the string. Format being : <constant variableName constant/>
Example patterns that it should match:
<tagGetIndexXYZ/>
<tagGetAllIndexXYZ/>
<tagGetFooterXYZ/>

The issue you have with Str.match(/<tag.*.XYZ\/>/g) is the .* takes everything it sees and does not stop at the XYZ as you wish. So you need to find a way to stop (e.g. the [^/]* means keep taking until you find a /) and then work back from there (the slice).
Does this help
testString = "<tagGetIndexXYZ/>"
res = testString.match(/<tag([^/]*)\/\>/)[1].slice(0,-3)
console.log(res)

Converting double backslash into backslash used for escaping?

I have a javascript string that contains \\n. When this is displayed out to a webpage, it shows literally as \n (as expected). I used text.replace(/\\n/g, '\n') to get it to act as a newline (which is the desired format).
I'm trying to determine the best way to catch all such instances (including similar instances like tabs \\t -> \t).
Is there a way to use regex (can't determine how to copy the matched wildcard letter to use in the replacement string) or anything else?

As mentioned by dandavis in the comments in original post, JSON.parse() ended up working for me.
i.e. text = JSON.parse(text);

Second answer, the first was wrong.
JavaScript works on a special way in this case. Read this for more details.
In your case it should be one of this ...
var JSCodeNewLine = "\u000A";
text.replace(/\\n/g, JSCodeNewLine);
var JSCodeCarriageReturnNewLine = "\u000D\u000A";
text.replace(/\\n/g, JSCodeCarriageReturnNewLine);

How do I extract the title value from a string using Javascript regexp?

I have a string variable which I would like to extract the title value in id="resultcount" element. The output should be 2.
var str = '<table cellpadding=0 cellspacing=0 width="99%" id="addrResults"><tr></tr></table><span id="resultcount" title="2" style="display:none;">2</span><span style="font-size: 10pt">2 matching results. Please select your address to proceed, or refine your search.</span>';
I tried the following regex but it is not working:
/id=\"resultcount\" title=['\"][^'\"](+['\"][^>]*)>/

Since var str = ... is Javascript syntax, I assume you need a Javascript solution. As Peter Corlett said, you can't parse HTML using regular expressions, but if you are using jQuery you can use it to take advantage of browser own parser without effort using this:
$('#resultcount', '<div>'+str+'</div>').attr('title')
It will return undefined if resultcount is not found or it has not a title attribute.

To make sure it doesn't matter which attribute (id or title) comes first in a string, take entire html element with required id:
var tag = str.replace(/^.*(<[^<]+?id=\"resultcount\".+?\/.+?>).*$/, "$1")
Then find title from previous string:
var res = tag.replace(/^.*title=\"(\d+)\".*$/, "$1");
// res is 2
But, as people have previously mentioned it is unreliable to use RegEx for parsing html, something as trivial as different quote (single instead of double quote) or space in "wrong" place will brake it.

Please see this earlier response, entitled "You can't parse [X]HTML with regex":
RegEx match open tags except XHTML self-contained tags

Well, since no one else is jumping in on this and I'm assuming you're just looking for a value and not trying to create a parser, I'll give you what works for me with PCRE. I'm not sure how to put it into the java format for you but I think you'll be able to do that.
span id="resultcount" title="(\d+)"
The part you're looking to get is the non-passive group $1 which is the '\d+' part. It will get one or more digits between the quote marks.