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Demonstrate the performance impact of using `instanceof` vs. checking for some existing property (in the megamorphic case)
// Copyright 2013-2019 Benedikt Meurer
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// <https://www.apache.org/licenses/LICENSE-2.0>
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
if (typeof console === 'undefined') console = {log:print};
const TESTS = [];
const A = function () {}
A.prototype = Object.create(null)
(function() {
const O = Object;
const hop = Object.hasOwnProperty
TESTS.push(
function instanceOf(a) {
return a instanceof O;
},
function nullOrConstructorOf(a) {
return a == null || a.constructor === O;
},
function instanceOfOrNull(a) {
return a instanceof O || a == null;
},
function nullOrInstanceOf(a) {
return a == null || a instanceof O;
},
function nullOrTypeofAndInstanceOf(a) {
return a == null || (typeof a === 'object' && a instanceof O);
},
function TypeofAndNullOrInstanceOf(a) {
return typeof a === 'object' && (a == null || a instanceof O);
},
function nullOrhasOwnProperty (a) {
return a == null || hop.call(a, 'constructor')
}
);
})();
const N = 1e6;
const objs = [
{a: 1}, // props
{b: 1}, // props
{c: 1}, // props
[], // children
'abc', // child
1234, // child
null, // props/child
undefined, // props/child
new A(), // vnode
new A(), // vnode
new A(), // vnode
new A(), // vnode
new A(), // vnode
new A(), // vnode
new A(), // vnode
new A(), // vnode
];
function test(fn) {
var result;
for (var i = 0; i < N; ++i) {
for (var j = 0; j < objs.length; ++j) {
result = fn(objs[j]);
}
}
return result;
}
test(x => x);
for (var j = 0; j < TESTS.length; ++j) {
test(TESTS[j]);
}
const perf = performance
for (var j = 0; j < TESTS.length; ++j) {
var startTime = perf.now();
test(TESTS[j]);
console.log(TESTS[j].name + ':', (perf.now() - startTime), 'ms.');
}
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