regex101: JavaScript Match Workspace

<iframethe literal text <iframe (case insensitive)

Negative Lookahead(?!<\/iframe>)

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

iframe>the literal text iframe> (case insensitive)

Character Class[\s\S]*?

*?matches any number of characters from the set below:

\sany whitespace character

\Sany non-whitespace character

data-contextthe literal text data-context (case insensitive)

Character Class[\s\S]*?

*?matches any number of characters from the set below:

\sany whitespace character

\Sany non-whitespace character

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

iframe>the literal text iframe> (case insensitive)

Global pattern flags

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

g modifier: global. Finds all matches instead of stopping after the first

Search reference

Regular Expression

<iframe(?!<\/iframe>)[\s\S]*?data-context[\s\S]*?<\/iframe>

New

<iframe src="http://youtube.com"></iframe> 

<iframe data-context="whatever" src="http://youtube.com"></iframe> 

<iframe src="http://youtube.com"></iframe> <iframe src="http://youtube.com"></iframe> 

<p>Potatoes are good</p>

<iframe src="http://youtube.com"></iframe> 

<iframe src="http://youtube.com" data-context="whatever"></iframe>

<iframe src="http://youtube.com"></iframe> 

<iframe src="http://instagram.com"></iframe>