Regex Practice 4/8

Anchors and boundaries

Lesson 1's hasCat matched "cat" inside "concatenate" - because by default a match can happen anywhere. Anchors fix that by pinning a match to a position instead of a character: ^ means "start of the string," $ means "end of the string." Wrap a pattern in ^...$ and it must match the entire string, not just some piece of it.

\b is a smaller version of the same idea: a word boundary, the edge between a word character and a non-word character (or the edge of the string). /\bcat\b/ matches "cat" as a whole word - in "the cat sat" - but not the cat buried inside "category".

Your task: write isWholeNumber(str), true only if the entire string is one or more digits, and hasWord(str), true if str contains "cat" as a whole word (not as part of a longer word).

You'll practice:

Anchoring a whole-string match with ^ and $
Matching a whole word (not a substring) with \b

// Write isWholeNumber(str): true only if str is entirely digits.
function isWholeNumber(str) {

}

// Write hasWord(str): true if str contains "cat" as a whole word.
function hasWord(str) {

}