Regular expression to remove spaces between invalid HTML tags - e.g. "</b>" should be "</b>"

Question

I have some HTML that is messed up by spaces within tags and want to make it valid again - for example:

< div class='test' >1 > 0 is < b >true</ b> and apples >>> bananas< / div >

should be converted to valid HTML, and when rendered, is expected to produce:

<code><div class='test'>1 > 0 is <b>true</b> and apples >>> bananas</div></code>

Any text preceded/followed by spaces in > or >< should remain unchanged - for example, ;1 > 0 should be retained instead of being compressed to 1>0

I realize this may require several regular expressions, which is fine

I have a few things:

<\s?\/\s* This will partially fix to< code>

Answer 1

There is no reasonable way to save a document as corrupted as what you posted, but assuming you replace the > and similar characters in the text with their related entities, e.g.: > ;, you can put the document you want to accept into an appropriate library, such as DomDocument which will handle the rest.

$input = <<<_E_
< div class='test' >1 > 0 is < b >true</ b> and apples >>> bananas< / div >
_E_;

$input = preg_replace([ '#<\s+#', '#</\s+#' ], [ '<', '</' ], $input);

$d = new DomDocument();
$d->loadHTML($input, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);

var_dump($d->saveHTML());

Output:

string(80) "<div class="test">1 > 0 is <b>true</b> and apples >>> bananas</div>"

Answer 2

This regular expression is also valid:

It divides the valid part in the HTML tag into four parts and replaces the remaining parts (spaces) with them.

Regex101 Demo

/(<)\s*(\/?)\s*([^<>]*\S)\s*(>)/g

• (<)<) - Capture the opening angle bracket (section 1)
• \s* - matches any whitespace
• (\/?) - Capturing optional backslashes (Part 2)
• \s* - matches any space after a backslash
• ([^<>]*\S) - captures content within tags without trailing spaces (section 3)
• \s* - Matches spaces after the content and before the closing angle bracket
• (>) - Capture right angle bracket (section 4)

const reg = /(<)\s*(\/?)\s*([^<>]*\S)\s*(>)/g
const str = "< div class='test' >1 > 0 is < b >true< / b > and apples >>> bananas< / div  >"
const newStr = str.replace(reg, "");
console.log(newStr);