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RegEx for matching style tag

I have an HTML code that contain CSS code inside tag under the header tag. I want to use regex to extract all text in HTML, only pure text (between HTML tags ). I tried,
console.log(HTML_TEXT.replace(/(<([^>]+)>)/g, ""))
which replace every thing between <> by empty char, the problem is the CSS code inside STYLE tag is still there, so i want to know how to write the regular expression to remove CSS code inside tags.
How do I solve this problem?

This RegEx might help you to do so:
(\>)(.+)(<\/style>)
It creates a right boundary in a capturing group: (<\/style>)
It has a left boundary in another capturing group: (\>), which you can add additional boundaries to it, if you wish/necessary
Then, it has a no-boundary middle capturing group, (.+), where your target is located, and you can call it using $2 and replace it with an empty string, or otherwise.
I'm not so sure, did not test it, but your code might look like something similar to:
console.log(HTML_TEXT.replace(/(\>)(.+)(<\/style>)/g, '\\$1\\$3'))
This post explains how to do a string replace in JavaScript.
Edit:
Based on the comment, this RegEx might help you to filter your tags using $1:
(\<style type=\"text\/css\"\>)([\s\S]*)(\<\/style\>)

JS Regex replacement - replace fixed text around random string

Given this text:
<span class='green'>foobar</span> something <span class='red'>fizzle</span>
I need to somehow attain this:
<tagA>foobar</tagA> something <tabB>fizzle</tagB>
I basically have to match <span class='green'>*anything*</span> and be able to differentiate it from the red one as well. I have to take this green span on both ends and replace it with a fixed string, but somehow retain whatever text is between the two tags.
I swear I've looked around a ton but have no idea how to find the solution for this with regex.

This should do the trick
Replace
<span class='green'>(.*?)</span>
With
<tagA>$1</tagA>
And do something similar for the class with the value red
Update 1
Response to feedback "What if something contains a newline?"
If I remember correctly JavaScript does not support the "single line mode" / Dot matches line breaks.
<span class='green'>([\s\S]*?)</span>
Update 2
This tweaked regex allows
<span\s+class\s*=\s*['"]green['"]\s*>([^>]*)</\s*span\s*>
white space where the html spec is allowing it
accepts single as well as double quotes for the attribute values
matches the value between the tags using a negated character class which is qualified greedy resulting in better performance generally and is also supported by JavaScript

Mustache.js allow only line breaks, escape other HTML

I am creating comments from user input and rendering them using Mustache.js after a user clicks 'submit'. I realize I can replace user input line breaks (\n) with <br/> to render as HTML breaks, such as
myString.replace(/\n/g, '<br />');
and I realize I can make Mustache not escape HTML by using triple brackets
{{{myString}}}
However, I would like to escape all user HTML as Mustache would typically do with double braces {{ ... }}, with the exception of allowing line breaks with <br/>
What is the best way to do this? I can replace the line breaks after it has been rendered, but that seems like a very inefficient solution, and I'm thinking there has to be a better way.

Option 1 - Use a pre tag:
It's actually best (or efficient) that you wrap text in a <pre></pre> tag, which will preserve the white space in the text.
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/pre
And enable word-wrap
How do I wrap text in a pre tag?
- http://jsfiddle.net/X5ZY7/
Option 2 - Split your string into lines, and use a mustache each:
comment = userComment.split("\n")
{{#comment}}
{{comment}}<br/>
{{/comment}}
Option 3 - Manually escape your string using your favorite method before injecting the tags:
var div = document.createElement("div")
div.textContent = comment
comment = div.innerHTML.replace(/\n/g, "<br/>")
{{{comment}}}

If you're looking to add line breaks to a textarea you need to replace \n with

Removing html line breaks using Javascript

I'm trying to grab an element's HTML using jQuery and then post it to the server. I successfully grabbed it, but I am not able to remove the white space between the tags and the line breaks that are rendered by default. The HTML code grabbed is shown below:
<table><tbody><tr><th></th><th>1</th><th>2</th><th>3</th><th>4</th><th>5</th><th>6</th><th>7</th></tr>
<tr><th>2nd row</th><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>
I would like to trim the spaces between the tags only. I've used this regular expression: str.replace(/\s+/g, ' ');. But that doesn't seem to work, any suggestions?

Currently, you are replacing all consecutive sequences of whitespace with a single space.
This is what you want:
str.replace(/>\s+</g, '><');

I need to add escape character(backslash - ) character at the end of each line to wrap the string.

How do I make the whitespace behaviour in a <textarea> and a HTML preview match?

I have a <textarea> element. When the user fills it, you can see the spaces they made and when they pressed Enter to jump to the next line.
This is great, but when I see the HTML output, the result differs. It is an endless sentence without line breaks.
Using only HTML or JavaScript, how can I fix this?

You probably want something like:
<p style="white-space: pre-wrap"></p>
<p style="white-space: pre"></p>
<pre></pre>
pre-wrap:
Whitespace is preserved by the browser. Text will wrap when necessary, and on line breaks
pre:
Whitespace is preserved by the browser. Text will only wrap on line breaks Acts like the <pre> tag in HTML

If you are just taking what is entered in a textarea and outputing it as html, you would see this. For starters, you could replace all spaces with and all newlines with <br>. Or put the output in <pre> tags. (In either case, you will also want to replace some other characters with entities too.)