ramda/src/adjust.js

var _concat =
/*#__PURE__*/
require("./internal/_concat");

var _curry3 =
/*#__PURE__*/
require("./internal/_curry3");
/**
 * Applies a function to the value at the given index of an array, returning a
 * new copy of the array with the element at the given index replaced with the
 * result of the function application.
 *
 * @func
 * @memberOf R
 * @since v0.14.0
 * @category List
 * @sig Number -> (a -> a) -> [a] -> [a]
 * @param {Number} idx The index.
 * @param {Function} fn The function to apply.
 * @param {Array|Arguments} list An array-like object whose value
 *        at the supplied index will be replaced.
 * @return {Array} A copy of the supplied array-like object with
 *         the element at index `idx` replaced with the value
 *         returned by applying `fn` to the existing element.
 * @see R.update
 * @example
 *
 *      R.adjust(1, R.toUpper, ['a', 'b', 'c', 'd']);      //=> ['a', 'B', 'c', 'd']
 *      R.adjust(-1, R.toUpper, ['a', 'b', 'c', 'd']);     //=> ['a', 'b', 'c', 'D']
 * @symb R.adjust(-1, f, [a, b]) = [a, f(b)]
 * @symb R.adjust(0, f, [a, b]) = [f(a), b]
 */


var adjust =
/*#__PURE__*/
_curry3(function adjust(idx, fn, list) {
  if (idx >= list.length || idx < -list.length) {
    return list;
  }

  var start = idx < 0 ? list.length : 0;

  var _idx = start + idx;

  var _list = _concat(list);

  _list[_idx] = fn(list[_idx]);
  return _list;
});

module.exports = adjust;