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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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41 changes: 23 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 +671,33 @@ 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 in value) {
if (visibleLength === ctx.maxArrayLength)
break;
const i = +elem;
if (index !== i) {
// Skip zero and negative numbers as well as non numbers
if (i > 0 === false)
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Can you add a comment on why this is necessary, and different from i <= 0? (I understand it because I saw an earlier version of the PR, but comments are more for future than now anyway.)

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Added

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 +813,7 @@ 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 +992,6 @@ function _extend(target, source) {
return target;
}

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


// Deprecated old stuff.

function print(...args) {
Expand Down
10 changes: 9 additions & 1 deletion test/parallel/test-util-inspect.js
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Original file line number Diff line number Diff line change
Expand Up @@ -298,8 +298,16 @@ 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 ]');
}

// Function with properties
Expand Down