ramda/src/adjust.js

A practical functional library for JavaScript programmers.

var _concat = /*#__PURE__*/require("./internal/_concat.js");
var _curry3 = /*#__PURE__*/require("./internal/_curry3.js");
/**
 * 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.
 *
 * When `idx < -list.length || idx >= list.length`, the original list is returned.
 *
 * @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']
 *
 *      // out-of-range returns original list
 *      R.adjust(4, R.toUpper, ['a', 'b', 'c', 'd']);      //=> ['a', 'b', 'c', 'd']
 *      R.adjust(-5, 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) {
  var len = list.length;
  if (idx >= len || idx < -len) {
    return list;
  }
  var _idx = (len + idx) % len;
  var _list = _concat(list);
  _list[_idx] = fn(list[_idx]);
  return _list;
});
module.exports = adjust;