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x/ramda/adjust.js

:ram: Practical functional Javascript
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import _concat from './internal/_concat';import _curry3 from './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 = _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;});export default adjust;