Text Processingflags: gi

Word Boundary (Whole Word Match)

Match the whole word `cat` without matching it inside other words like `concatenate` or `category`.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("\\bcat\\b", "gi");
const input = "The cat sat on the mat.";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"\bcat\b", re.IGNORECASE)
input_text = "The cat sat on the mat."
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

Go (RE2) code

goGo

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`(?i)\bcat\b`)
	input := `The cat sat on the mat.`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.

Pattern

regexengine-agnostic

\bcat\b   (flags: gi)

Raw source: \bcat\b

How it works

\b is a zero-width assertion at a word boundary — the position between a word character (\w) and a non-word character (or string edge). Wrapping `cat` in two \b anchors forces the match to start AND end at word boundaries, so `cat` matches but `concat` and `cats` do not.