Javascript Regex: Match any series of letters, unless they match a specific sequence -

i want match sequence of letters, except if match specific, unwanted sequence.

so example, if sentence is:

this cat.

and want include letters except sequence cat, how write in regex?

i've tried (?!cat)([a-z])+ matches c. need match entire cat , exclude that. i've tried \b word boundaries well, no success.

\b(?:(?!\bcat\b)[a-za-z])+\b

try this.see demo.

Fun enginering