freeCodeCamp/curriculum/challenges/en/08-coding-interview-prep/rosetta-code/count-occurrences-of-a-substring.en.md

title, id, challengeType

title	id	challengeType
Count occurrences of a substring	596fda99c69f779975a1b67d	5

Description

Task:

Create a function, or show a built-in function, to count the number of non-overlapping occurrences of a substring inside a string.

The function should take two arguments:

the first argument being the string to search, and the second a substring to be searched for.

It should return an integer count.

The matching should yield the highest number of non-overlapping matches.

In general, this essentially means matching from left-to-right or right-to-left.

Instructions

Tests

- text: <code>countSubstring</code> is a function.
  testString: 'assert(typeof countSubstring === ''function'', ''<code>countSubstring</code> is a function.'');'
- text: '<code>countSubstring("the three truths", "th")</code> should return <code>3</code>.'
  testString: 'assert.equal(countSubstring(testCases[0], searchString[0]), results[0], ''<code>countSubstring("the three truths", "th")</code> should return <code>3</code>.'');'
- text: '<code>countSubstring("ababababab", "abab")</code> should return <code>2</code>.'
  testString: 'assert.equal(countSubstring(testCases[1], searchString[1]), results[1], ''<code>countSubstring("ababababab", "abab")</code> should return <code>2</code>.'');'
- text: '<code>countSubstring("abaabba*bbaba*bbab", "a*b")</code> should return <code>2</code>.'
  testString: 'assert.equal(countSubstring(testCases[2], searchString[2]), results[2], ''<code>countSubstring("abaabba*bbaba*bbab", "a*b")</code> should return <code>2</code>.'');'

Challenge Seed

function countSubstring (str, subStr) {
  // Good luck!
  return true;
}

After Test

console.info('after the test');

Solution

function countSubstring(str, subStr) {
  const escapedSubStr = subStr.replace(/[.+*?^$[\]{}()|/]/g, '\\$&');
  const matches = str.match(new RegExp(escapedSubStr, 'g'));
  return matches ? matches.length : 0;
}