https://www.w3schools.com:443/jsref/met_domtokenlist_contains.asp
HTML DOMTokenList contains() Method
Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML...
html domtokenlistcontainsmethod
https://www.w3schools.com:443/jsref/met_domtokenlist_keys.asp
HTML DOMTokenList keys() Method
Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML...
html domtokenlistkeysmethod