Count number of matches of a regex in Javascript

Question

I wanted to write a regex to count the number of spaces/tabs/newline in a chunk of text. So I naively wrote the following:-

numSpaces : function(text) { 
    return text.match(/s/).length; 
}

For some unknown reasons it always returns 1. What is the problem with the above statement? I have since solved the problem with the following:-

numSpaces : function(text) { 
    return (text.split(/s/).length -1); 
}

Answer 1

tl;dr: Generic Pattern Counter

// THIS IS WHAT YOU NEED
const count = (str) => {
  const re = /YOUR_PATTERN_HERE/g
  return ((str || '').match(re) || []).length
}

For those that arrived here looking for a generic way to count the number of occurrences of a regex pattern in a string, and don't want it to fail if there are zero occurrences, this code is what you need. Here's a demonstration:

/*
 *  Example
 */

const count = (str) => {
  const re = /[a-z]{3}/g
  return ((str || '').match(re) || []).length
}

const str1 = 'abc, def, ghi'
const str2 = 'ABC, DEF, GHI'

console.log(`'${str1}' has ${count(str1)} occurrences of pattern '/[a-z]{3}/g'`)
console.log(`'${str2}' has ${count(str2)} occurrences of pattern '/[a-z]{3}/g'`)