Javascript对象与地图性能(Chrome,V8,Node JS)

Question

Javascript对象与地图性能(Chrome,V8,Node JS)

我想要了解是否使用JS对象或地图,如果我需要在大型数据集(> 1000个对象)中按字符串键进行随机查找.

我写了一个简单的基准http://jsperf.com/javascript-objects-vs-map-performance,结果显示在Chrome(V8)中,对象的表现比你好大约2倍.但是,我检查了其他浏览器,结果则相反.为什么它们在各种浏览器/引擎中有所不同？

我还在Node.JS中编写了类似的测试,我看不到类似的结果(测试用例6比测试用例4要多得多):

测试

var now = require("performance-now");

var mapKeyValue = new Map();
var mapStringKeyValue = new Map();
var objectKeyValue = {};
var n = 10000;
var testSamples = 100;

var firstRow = 0;
var firstRowString = firstRow + "";

var middleRow = Math.floor(n / 2);
var middleRowString = middleRow + "";

var lastRow = n - 1;
var lastRowString = lastRow + "";

var nonExist = n * 2;
var nonExistString = nonExist + "";

function makeid() {
  var text = "";
  var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

  for (var i = 0; i < 20; i++)
    text += possible.charAt(Math.floor(Math.random() * possible.length));

  return text;
}

for (var i = 0; i < n; i++) {
  var value = makeid();
  mapKeyValue.set(i, value);
  mapStringKeyValue.set(i + "", value);
  objectKeyValue[i + ""] = value;
}

var t0, t1;

var averages = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

for (var j = 0; j < testSamples; j++) {
  var k = 0;
  t0 = now();
  mapKeyValue.get(firstRow);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  mapStringKeyValue.get(firstRowString);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  objectKeyValue[firstRowString];
  t1 = now();
  averages[k++] += (t1 - t0);


  t0 = now();
  mapKeyValue.get(middleRow);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  mapStringKeyValue.get(middleRowString);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  objectKeyValue[middleRowString];
  t1 = now();
  averages[k++] += (t1 - t0);


  t0 = now();
  mapKeyValue.get(lastRow);
  t1 = now();
  averages[k++] += (t1 - t0);


  t0 = now();
  mapStringKeyValue.get(lastRowString);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  objectKeyValue[lastRowString];
  t1 = now();
  averages[k++] += (t1 - t0);


  t0 = now();
  mapKeyValue.get(nonExist);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  mapStringKeyValue.get(nonExistString);
  t1 = now();
  averages[k++] += (t1 - t0);

  t0 = now();
  objectKeyValue[nonExistString];
  t1 = now();
  averages[k++] += (t1 - t0);
}

console.log("Test samples number " + testSamples);

for (var i = 0; i < averages.length; i++) {
  averages[i] /= testSamples;
  console.log("Test case " + (i + 1) + " took in average " + (averages[i] * 1000000) + " ns");
}

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结果

Test samples number 100
Test case 1 took in average 2050.269999999692 ns
Test case 2 took in average 751.2899999997202 ns
Test case 3 took in average 567.3000000004081 ns
Test case 4 took in average 727.2699999999688 ns
Test case 5 took in average 4760.029999999489 ns
Test case 6 took in average 1939.3400000004135 ns
Test case 7 took in average 673.549999999885 ns
Test case 8 took in average 689.3600000002564 ns
Test case 9 took in average 541.3700000001143 ns
Test case 10 took in average 1146.0599999999843 ns
Test case 11 took in average 3096.7699999998285 ns
Test case 12 took in average 644.7400000000058 ns

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如果您对如何改进基准测试并使其更准确,请告诉我.谢谢.