adjust.js•1.22 kB
var _concat = require('./internal/_concat');
var _curry3 = 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 (a -> a) -> Number -> [a] -> [a]
* @param {Function} fn The function to apply.
* @param {Number} idx The index.
* @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(R.add(10), 1, [0, 1, 2]); //=> [0, 11, 2]
* R.adjust(R.add(10))(1)([0, 1, 2]); //=> [0, 11, 2]
*/
module.exports = _curry3(function adjust(fn, idx, 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;
});