splitWhen.js•1.05 kB
var _curry2 = require('./internal/_curry2');
var _slice = require('./internal/_slice');
/**
* Takes a list and a predicate and returns a pair of lists with the following properties:
*
* - the result of concatenating the two output lists is equivalent to the input list;
* - none of the elements of the first output list satisfies the predicate; and
* - if the second output list is non-empty, its first element satisfies the predicate.
*
* @func
* @memberOf R
* @since v0.19.0
* @category List
* @sig (a -> Boolean) -> [a] -> [[a], [a]]
* @param {Function} pred The predicate that determines where the array is split.
* @param {Array} list The array to be split.
* @return {Array}
* @example
*
* R.splitWhen(R.equals(2), [1, 2, 3, 1, 2, 3]); //=> [[1], [2, 3, 1, 2, 3]]
*/
module.exports = _curry2(function splitWhen(pred, list) {
var idx = 0;
var len = list.length;
var prefix = [];
while (idx < len && !pred(list[idx])) {
prefix.push(list[idx]);
idx += 1;
}
return [prefix, _slice(list, idx)];
});