module.exports = function strspn(str1, str2, start, lgth) {
  //  discuss at: https://locutus.io/php/strspn/
  // original by: Valentina De Rosa
  // improved by: Brett Zamir (https://brett-zamir.me)
  //   example 1: strspn('42 is the answer, what is the question ...', '1234567890')
  //   returns 1: 2
  //   example 2: strspn('foo', 'o', 1, 2)
  //   returns 2: 2

  let found
  let stri
  let strj
  let j = 0
  let i = 0

  start = start ? (start < 0 ? str1.length + start : start) : 0
  lgth = lgth ? (lgth < 0 ? str1.length + lgth - start : lgth) : str1.length - start
  str1 = str1.substr(start, lgth)

  for (i = 0; i < str1.length; i++) {
    found = 0
    stri = str1.substring(i, i + 1)
    for (j = 0; j <= str2.length; j++) {
      strj = str2.substring(j, j + 1)
      if (stri === strj) {
        found = 1
        break
      }
    }
    if (found !== 1) {
      return i
    }
  }

  return i
}