Regular expression to match a word or its prefix

Question

I want to match a regular expression on a whole word.

In the following example I am trying to match s or season but what I have matches

Answer 1

I test examples in js. Simplest solution - just add word u need inside / /:

var reg = /cat/;
reg.test('some cat here');//1 test
true // result
reg.test('acatb');//2 test
true // result

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Now if u need this specific word with boundaries, not inside any other signs-letters. We use b marker:

var reg = /\bcat\b/
reg.test('acatb');//1 test 
false // result
reg.test('have cat here');//2 test
true // result

We have also exec() method in js, whichone returns object-result. It helps f.g. to get info about place/index of our word.

var matchResult = /\bcat\b/.exec("good cat good");
console.log(matchResult.index); // 5

If we need get all matched words in string/sentence/text, we can use g modifier (global match):

"cat good cat good cat".match(/\bcat\b/g).length
// 3 

Now the last one - i need not 1 specific word, but some of them. We use | sign, it means choice/or.

"bad dog bad".match(/\bcat|dog\b/g).length
// 1