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util: improve util.inspect performance #14492

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util: improve util.inspect performance #14492

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ddd4de4
util: use for in instead of while hasOwnProperty
BridgeAR Jul 26, 2017
b73a399
util: use faster visibleKeys property lookup
BridgeAR Jul 26, 2017
ab497df
fixup
BridgeAR Jul 26, 2017
61119e4
fixup comments commit 1
BridgeAR Jul 27, 2017
a2574f0
fixup commit 1
BridgeAR Jul 28, 2017
4aed280
benchmarks: add inspect-array benchmark
BridgeAR Jul 28, 2017
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39 changes: 39 additions & 0 deletions benchmark/util/inspect-array.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,39 @@
'use strict';

const common = require('../common');
const util = require('util');

const bench = common.createBenchmark(main, {
n: [1e2],
len: [1e5],
type: [
'denseArray',
'sparseArray',
'mixedArray'
]
});

function main(conf) {
const { n, len, type } = conf;
var arr = Array(len);
var i;

switch (type) {
case 'denseArray':
arr = arr.fill(0);
break;
case 'sparseArray':
break;
case 'mixedArray':
for (i = 0; i < n; i += 2)
arr[i] = i;
break;
default:
throw new Error(`Unsupported type ${type}`);
}
bench.start();
for (i = 0; i < n; i++) {
util.inspect(arr);
}
bench.end(n);
}
44 changes: 26 additions & 18 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,6 @@ const inspectDefaultOptions = Object.seal({

const numbersOnlyRE = /^\d+$/;

const objectHasOwnProperty = Object.prototype.hasOwnProperty;
const propertyIsEnumerable = Object.prototype.propertyIsEnumerable;
const regExpToString = RegExp.prototype.toString;
const dateToISOString = Date.prototype.toISOString;
Expand Down Expand Up @@ -672,22 +671,36 @@ function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
var output = [];
let visibleLength = 0;
let index = 0;
while (index < value.length && visibleLength < ctx.maxArrayLength) {
let emptyItems = 0;
while (index < value.length && !hasOwnProperty(value, String(index))) {
emptyItems++;
index++;
}
if (emptyItems > 0) {
for (const elem of keys) {
if (visibleLength === ctx.maxArrayLength)
break;
// Symbols might have been added to the keys
if (typeof elem !== 'string')
continue;
const i = +elem;
if (index !== i) {
// Skip zero and negative numbers as well as non numbers
if (i > 0 === false)
continue;
const emptyItems = i - index;
const ending = emptyItems > 1 ? 's' : '';
const message = `<${emptyItems} empty item${ending}>`;
output.push(ctx.stylize(message, 'undefined'));
} else {
output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
String(index), true));
index++;
index = i;
if (++visibleLength === ctx.maxArrayLength)
break;
}
output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
elem, true));
visibleLength++;
index++;
}
if (index < value.length && visibleLength !== ctx.maxArrayLength) {
const len = value.length - index;
const ending = len > 1 ? 's' : '';
const message = `<${len} empty item${ending}>`;
output.push(ctx.stylize(message, 'undefined'));
index = value.length;
}
var remaining = value.length - index;
if (remaining > 0) {
Expand Down Expand Up @@ -803,7 +816,7 @@ function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
str = ctx.stylize('[Setter]', 'special');
}
}
if (!hasOwnProperty(visibleKeys, key)) {
if (visibleKeys[key] === undefined) {
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It may be worth to eventually make visibleKeys an ES2015 Set instead of emulating it via an object, but I don't know how it will affect performance with the current V8 (if it will at all).

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@BridgeAR BridgeAR Jul 28, 2017 •
edited
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When I looked at the code there were a couple more optimizations possible but I tried to be more surgical here. E.g. for arrays there is no need for Object.keys when using for in and ctx.seen should be a Set instead of an Array.

if (typeof key === 'symbol') {
name = `[${ctx.stylize(key.toString(), 'symbol')}]`;
} else {
Expand Down Expand Up @@ -982,11 +995,6 @@ function _extend(target, source) {
return target;
}

function hasOwnProperty(obj, prop) {
return objectHasOwnProperty.call(obj, prop);
}


// Deprecated old stuff.

function print(...args) {
Expand Down
18 changes: 17 additions & 1 deletion test/parallel/test-util-inspect.js
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Expand Up @@ -298,8 +298,24 @@ assert.strictEqual(
get: function() { this.push(true); return this.length; }
}
);
Object.defineProperty(
value,
'-1',
{
enumerable: true,
value: -1
}
);
assert.strictEqual(util.inspect(value),
'[ 1, 2, 3, growingLength: [Getter] ]');
'[ 1, 2, 3, growingLength: [Getter], \'-1\': -1 ]');
}

// Array with inherited number properties
{
class CustomArray extends Array {};
CustomArray.prototype[5] = 'foo';
const arr = new CustomArray(50);
assert.strictEqual(util.inspect(arr), 'CustomArray [ <50 empty items> ]');
}

// Function with properties
Expand Down