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MapConstructor.js
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63 lines (57 loc) · 2.66 KB
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/*
* Copyright (C) 2023 Devin Rousso <webkit@devinrousso.com>.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
function groupBy(items, callback)
{
"use strict";
if (@isUndefinedOrNull(items))
@throwTypeError("Map.groupBy requires that the first argument not be null or undefined");
if (!@isCallable(callback))
@throwTypeError("Map.groupBy requires that the second argument must be a function");
var iteratorMethod = items.@@iterator;
if (!@isCallable(iteratorMethod))
@throwTypeError("Map.groupBy requires that the property of the first argument, items[Symbol.iterator] be a function");
var groups = new @Map;
var k = 0;
var iterator = iteratorMethod.@call(items);
// Since for-of loop once more looks up the @@iterator property of a given iterable,
// it could be observable if the user defines a getter for @@iterator.
// To avoid this situation, we define a wrapper object that @@iterator just returns a given iterator.
var wrapper = {
@@iterator: function () { return iterator; }
};
for (var item of wrapper) {
if (k >= @MAX_SAFE_INTEGER)
@throwTypeError("The number of iterations exceeds 2**53 - 1");
var key = callback.@call(@undefined, item, k);
var group = groups.@get(key);
if (!group) {
group = [];
groups.@set(key, group);
}
@putByValDirect(group, group.length, item);
++k;
}
return groups;
}