31 lines
681 B
Plaintext
31 lines
681 B
Plaintext
|
/**
|
||
|
|
* Copyright (c) 2013-present, Facebook, Inc.
|
||
|
|
*
|
||
|
|
* This source code is licensed under the MIT license found in the
|
||
|
|
* LICENSE file in the root directory of this source tree.
|
||
|
|
*
|
||
|
|
* @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;
|