Function _setSubstring

src/function/matrix/subset.js:185–241

* Replace a substring in a string * @param {string} str string to be replaced * @param {Index} index An index or list of indices (character positions) * @param {string} replacement Replacement string * @param {string} [defaultValue] Default value to be used when resizing

(str, index, replacement, defaultValue)

 * @private
 */
function _setSubstring (str, index, replacement, defaultValue) {
  if (!index || index.isIndex !== true) {
    // TODO: better error message
    throw new TypeError('Index expected')
  }
  if (isEmptyIndex(index)) { return str }
  validateIndexSourceSize(Array.from(str), index)
  if (index.size().length !== 1) {
    throw new DimensionError(index.size().length, 1)
  }
  if (defaultValue !== undefined) {
    if (typeof defaultValue !== 'string' || defaultValue.length !== 1) {
      throw new TypeError('Single character expected as defaultValue')
    }
  } else {
    defaultValue = ' '
  }

  const range = index.dimension(0)
  const len = Number.isInteger(range) ? 1 : range.size()[0]

  if (len !== replacement.length) {
    throw new DimensionError(range.size()[0], replacement.length)
  }

  // validate whether the range is out of range
  const strLen = str.length
  validateIndex(index.min()[0])
  validateIndex(index.max()[0])

  // copy the string into an array with characters
  const chars = []
  for (let i = 0; i < strLen; i++) {
    chars[i] = str.charAt(i)
  }

  function callback (v, i) {
    chars[v] = replacement.charAt(i[0])
  }

  if (Number.isInteger(range)) {
    callback(range, [0])
  } else {
    range.forEach(callback)
  }

  // initialize undefined characters with a space
  if (chars.length > strLen) {
    for (let i = strLen - 1, len = chars.length; i < len; i++) {
      if (!chars[i]) {
        chars[i] = defaultValue
      }
    }
  }

  return chars.join('')
}