22 lines
755 B
JavaScript
22 lines
755 B
JavaScript
'use strict';
|
|
var $ = require('../internals/export');
|
|
var iterate = require('../internals/iterate');
|
|
var aFunction = require('../internals/a-function');
|
|
|
|
// `Map.groupBy` method
|
|
// https://github.com/tc39/proposal-collection-methods
|
|
$({ target: 'Map', stat: true }, {
|
|
groupBy: function groupBy(iterable, keyDerivative) {
|
|
var newMap = new this();
|
|
aFunction(keyDerivative);
|
|
var has = aFunction(newMap.has);
|
|
var get = aFunction(newMap.get);
|
|
var set = aFunction(newMap.set);
|
|
iterate(iterable, function (element) {
|
|
var derivedKey = keyDerivative(element);
|
|
if (!has.call(newMap, derivedKey)) set.call(newMap, derivedKey, [element]);
|
|
else get.call(newMap, derivedKey).push(element);
|
|
});
|
|
return newMap;
|
|
}
|
|
});
|