closure-benchmark.js

var outerVars = 10000
var iterations = 100000

src = ''
src += '(function() {'
for (var i = 0; i < outerVars / 3; i++) {
  src += '  var num' + i + ' = 1\n'
  src += '  var read' + i + ' = function() {\n'
  // Prevent inlining by feigning recursion
  src += '    if (!num' + i + ') read' + i + '()\n'
  src += '    return num' + i + '\n'
  src += '  }\n'
  src += '  var write' + i + ' = function() {\n'
  // Prevent inlining by feigning recursion
  src += '    if (!num' + i + ') write' + i + '()\n'
  src += '    num' + i + ' = num' + i + '\n'
  src += '  }\n'
}
src += '  console.time("test")\n'
// On Node but not Chrome stable, performance is O(outerVars**2). It is not
// related to the number of iterations in this loop, as long as iterations >=
// 23557 (on my system). Below that magic number, execution time drops to O(1)
// <1ms.
src += '  for (var i = 0; i < ' + iterations + '; i++) {\n'
src += '    write0()\n'
src += '    read0()\n'
src += '  }\n'
src += '  console.timeEnd("test")\n'
src += '})()\n'

eval(src)