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@bmeurer
Last active November 17, 2016 06:09
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Destructuring performace (V8 ToT 2016/11/16)
/////////////////////////////////////////////////////////////////////////////
// Test framework:
// Warmup
for (var i = 0; i < 1000; ++i) test(data);
function time(test, a) {
let startTime = Date.now();
// Using F.p.apply here to prevent inlining, so we can really
// just measure the performance of test stand-alone.
for (let i = 0; i < 5000000; ++i) test.apply(undefined, [a]);
let endTime = Date.now();
print("Time: " + (endTime - startTime) + "ms.");
}
time(test, data);
/////////////////////////////////////////////////////////////////////////////
// Test data (Source: https://fhinkel.github.io/six-speed)
var data = {
a: 'foo',
b: {c: 'd'},
arr: [1, 2, 3]
};
/////////////////////////////////////////////////////////////////////////////
// Naive ES5 version (Source: https://fhinkel.github.io/six-speed)
function test(data) {
var a = data.a,
b = data.b.c,
c = data.arr[1];
return c;
}
/////////////////////////////////////////////////////////////////////////////
// ES6 destructuring version (Source: https://fhinkel.github.io/six-speed)
function test(data) {
var {a, b:{c:b}, arr:[, c]} = data;
return c;
}
/////////////////////////////////////////////////////////////////////////////
// Results (with experimental TurboFan escape analysis):
//
// $ d8 --turbo-escape destructuring.es5
// Time: 275ms.
//
// $ d8 --turbo-escape destructuring.es6
// Time: 344ms.
//
// State: 20% missing for ES6 version to reach parity.
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