voca/count_substrings.js

The ultimate JavaScript string library

'use strict';

require('./internal/is_nil.js');
require('./is_string.js');
var coerce_to_string = require('./internal/coerce_to_string.js');

/**
 * Counts the number of `substring` appearances in `subject`.
 *
 * @function countSubstrings
 * @static
 * @since 1.0.0
 * @memberOf Count
 * @param  {string} [subject=''] The string where to count.
 * @param  {string} substring    The substring to be counted.
 * @return {number}              Returns the number of `substring` appearances.
 * @example
 * v.countSubstrings('bad boys, bad boys whatcha gonna do?', 'boys');
 * // => 2
 *
 * v.countSubstrings('every dog has its day', 'cat');
 * // => 0
 */

function countSubstrings(subject, substring) {
  var subjectString = coerce_to_string.coerceToString(subject);
  var substringString = coerce_to_string.coerceToString(substring);
  var substringLength = substringString.length;
  var count = 0;
  var matchIndex = 0;

  if (subjectString === '' || substringString === '') {
    return count;
  }

  do {
    matchIndex = subjectString.indexOf(substringString, matchIndex);

    if (matchIndex !== -1) {
      count++;
      matchIndex += substringLength;
    }
  } while (matchIndex !== -1);

  return count;
}

module.exports = countSubstrings;