/** * Copyright (c) 2013-present, Facebook, Inc. * All rights reserved. * * This source code is licensed under the BSD-style license found in the * LICENSE file in the root directory of this source tree. An additional grant * of patent rights can be found in the PATENTS file in the same directory. * * @providesModule countDistinct * @flow */ 'use strict'; var Set = require('./Set'); var emptyFunction = require('./emptyFunction'); /** * Returns the count of distinct elements selected from an array. */ function countDistinct<T1, T2>(iter: Iterable<T1>, selector: (item: T1) => T2): number { selector = selector || emptyFunction.thatReturnsArgument; var set = new Set(); for (var val of iter) { set.add(selector(val)); } return set.size; } module.exports = countDistinct;