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feat: add maxArrayLength option #51

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feat: add maxArrayLength option #51

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a88b6ab
feat: add maxArrayLength option
abhu85 Feb 23, 2026
87ccc38
chore: retrigger CI after GitHub infrastructure failure
abhu85 Mar 9, 2026
b9bb414
chore: retrigger CI after GitHub infrastructure failures
abhu85 Mar 9, 2026
c2ec95d
refactor: improve maxArrayLength validation readability and add exten…
abhu85 Mar 14, 2026
fc4b480
fix: support TypedArrays and arguments, optimize Map/Set iteration
abhu85 Mar 15, 2026
f0498df
Merge branch 'main' into add-maxArrayLength-option
abhu85 Mar 15, 2026
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122 changes: 112 additions & 10 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,12 @@ var hasMap = typeof Map === 'function' && Map.prototype;
var mapSizeDescriptor = Object.getOwnPropertyDescriptor && hasMap ? Object.getOwnPropertyDescriptor(Map.prototype, 'size') : null;
var mapSize = hasMap && mapSizeDescriptor && typeof mapSizeDescriptor.get === 'function' ? mapSizeDescriptor.get : null;
var mapForEach = hasMap && Map.prototype.forEach;
var mapEntries = hasMap && Map.prototype.entries;
var hasSet = typeof Set === 'function' && Set.prototype;
var setSizeDescriptor = Object.getOwnPropertyDescriptor && hasSet ? Object.getOwnPropertyDescriptor(Set.prototype, 'size') : null;
var setSize = hasSet && setSizeDescriptor && typeof setSizeDescriptor.get === 'function' ? setSizeDescriptor.get : null;
var setForEach = hasSet && Set.prototype.forEach;
var setValues = hasSet && Set.prototype.values;
var hasWeakMap = typeof WeakMap === 'function' && WeakMap.prototype;
var weakMapHas = hasWeakMap ? WeakMap.prototype.has : null;
var hasWeakSet = typeof WeakSet === 'function' && WeakSet.prototype;
Expand Down Expand Up @@ -112,6 +114,21 @@ module.exports = function inspect_(obj, options, depth, seen) {
}
var numericSeparator = opts.numericSeparator;

if (
has(opts, 'maxArrayLength')
&& opts.maxArrayLength !== null
&& opts.maxArrayLength !== Infinity
&& (
typeof opts.maxArrayLength !== 'number'
|| opts.maxArrayLength < 0
|| opts.maxArrayLength !== opts.maxArrayLength // NaN
|| parseInt(opts.maxArrayLength, 10) !== opts.maxArrayLength // non-integer
)
) {
throw new TypeError('option "maxArrayLength", if provided, must be a non-negative integer, Infinity, or `null`');
}
var maxArrayLength = typeof opts.maxArrayLength === 'number' ? opts.maxArrayLength : Infinity;

if (typeof obj === 'undefined') {
return 'undefined';
}
Expand Down Expand Up @@ -190,12 +207,45 @@ module.exports = function inspect_(obj, options, depth, seen) {
}
if (isArray(obj)) {
if (obj.length === 0) { return '[]'; }
var xs = arrObjKeys(obj, inspect);
var xs = arrObjKeys(obj, inspect, maxArrayLength);
if (indent && !singleLineValues(xs)) {
return '[' + indentedJoin(xs, indent) + ']';
}
return '[ ' + $join.call(xs, ', ') + ' ]';
}
if (isTypedArray(obj)) {
var typedTag = $slice.call(toStr(obj), 8, -1); // e.g., 'Uint8Array'
if (obj.length === 0) { return typedTag + ' []'; }
var typedXs = [];
var typedLimit = maxArrayLength < obj.length ? maxArrayLength : obj.length;
for (var ti = 0; ti < typedLimit; ti++) {
typedXs.push(String(obj[ti]));
}
if (obj.length > maxArrayLength) {
var typedRemaining = obj.length - maxArrayLength;
typedXs.push('... ' + typedRemaining + ' more item' + (typedRemaining > 1 ? 's' : ''));
}
if (indent && !singleLineValues(typedXs)) {
return typedTag + ' [' + indentedJoin(typedXs, indent) + ']';
}
return typedTag + ' [ ' + $join.call(typedXs, ', ') + ' ]';
}
if (isArguments(obj)) {
if (obj.length === 0) { return 'Arguments []'; }
var argXs = [];
var argLimit = maxArrayLength < obj.length ? maxArrayLength : obj.length;
for (var ai = 0; ai < argLimit; ai++) {
argXs.push(has(obj, ai) ? inspect(obj[ai], obj) : '');
}
if (obj.length > maxArrayLength) {
var argRemaining = obj.length - maxArrayLength;
argXs.push('... ' + argRemaining + ' more item' + (argRemaining > 1 ? 's' : ''));
}
if (indent && !singleLineValues(argXs)) {
return 'Arguments [' + indentedJoin(argXs, indent) + ']';
}
return 'Arguments [ ' + $join.call(argXs, ', ') + ' ]';
}
if (isError(obj)) {
var parts = arrObjKeys(obj, inspect);
if (!('cause' in Error.prototype) && 'cause' in obj && !isEnumerable.call(obj, 'cause')) {
Expand All @@ -213,21 +263,53 @@ module.exports = function inspect_(obj, options, depth, seen) {
}
if (isMap(obj)) {
var mapParts = [];
if (mapForEach) {
var mapLen = mapSize.call(obj);
var mapCount = 0;
if (mapEntries) {
var mapIter = mapEntries.call(obj);
var mapEntry;
while (mapCount < maxArrayLength && !(mapEntry = mapIter.next()).done) {
mapParts.push(inspect(mapEntry.value[0], obj, true) + ' => ' + inspect(mapEntry.value[1], obj));
mapCount += 1;
}
} else if (mapForEach) {
mapForEach.call(obj, function (value, key) {
mapParts.push(inspect(key, obj, true) + ' => ' + inspect(value, obj));
if (mapCount < maxArrayLength) {
mapParts.push(inspect(key, obj, true) + ' => ' + inspect(value, obj));
}
Comment on lines +277 to +279
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@ljharb ljharb Mar 14, 2026

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The map/set callbacks still run for every entry; they just skip the push when mapCount >= maxArrayLength. For a Map with 100k entries and maxArrayLength: 5, all 100k entries are still visited (and their keys/values are still inspected). We'd need to use a while loop over .next() to actually get a performance benefit here.

mapCount += 1;
});
}
return collectionOf('Map', mapSize.call(obj), mapParts, indent);
if (mapLen > maxArrayLength) {
var mapRemaining = mapLen - maxArrayLength;
mapParts.push('... ' + mapRemaining + ' more item' + (mapRemaining > 1 ? 's' : ''));
}
return collectionOf('Map', mapLen, mapParts, indent);
}
if (isSet(obj)) {
var setParts = [];
if (setForEach) {
var setLen = setSize.call(obj);
var setCount = 0;
if (setValues) {
var setIter = setValues.call(obj);
var setEntry;
while (setCount < maxArrayLength && !(setEntry = setIter.next()).done) {
setParts.push(inspect(setEntry.value, obj));
setCount += 1;
}
} else if (setForEach) {
setForEach.call(obj, function (value) {
setParts.push(inspect(value, obj));
if (setCount < maxArrayLength) {
setParts.push(inspect(value, obj));
}
setCount += 1;
});
}
return collectionOf('Set', setSize.call(obj), setParts, indent);
if (setLen > maxArrayLength) {
var setRemaining = setLen - maxArrayLength;
setParts.push('... ' + setRemaining + ' more item' + (setRemaining > 1 ? 's' : ''));
}
return collectionOf('Set', setLen, setParts, indent);
}
if (isWeakMap(obj)) {
return weakCollectionOf('WeakMap');
Expand Down Expand Up @@ -297,6 +379,21 @@ function isError(obj) { return toStr(obj) === '[object Error]' && canTrustToStri
function isString(obj) { return toStr(obj) === '[object String]' && canTrustToString(obj); }
function isNumber(obj) { return toStr(obj) === '[object Number]' && canTrustToString(obj); }
function isBoolean(obj) { return toStr(obj) === '[object Boolean]' && canTrustToString(obj); }
function isArguments(obj) { return toStr(obj) === '[object Arguments]'; }
function isTypedArray(obj) {
var tag = toStr(obj);
return tag === '[object Int8Array]'
|| tag === '[object Uint8Array]'
|| tag === '[object Uint8ClampedArray]'
|| tag === '[object Int16Array]'
|| tag === '[object Uint16Array]'
|| tag === '[object Int32Array]'
|| tag === '[object Uint32Array]'
|| tag === '[object Float32Array]'
|| tag === '[object Float64Array]'
|| tag === '[object BigInt64Array]'
|| tag === '[object BigUint64Array]';
}

// Symbol and BigInt do have Symbol.toStringTag by spec, so that can't be used to eliminate false positives
function isSymbol(obj) {
Expand Down Expand Up @@ -503,14 +600,19 @@ function indentedJoin(xs, indent) {
return lineJoiner + $join.call(xs, ',' + lineJoiner) + '\n' + indent.prev;
}

function arrObjKeys(obj, inspect) {
function arrObjKeys(obj, inspect, maxLength) {
var isArr = isArray(obj);
var xs = [];
if (isArr) {
xs.length = obj.length;
for (var i = 0; i < obj.length; i++) {
var limit = typeof maxLength === 'number' && maxLength < obj.length ? maxLength : obj.length;
xs.length = limit;
for (var i = 0; i < limit; i++) {
xs[i] = has(obj, i) ? inspect(obj[i], obj) : '';
}
if (typeof maxLength === 'number' && obj.length > maxLength) {
var remaining = obj.length - maxLength;
xs.push('... ' + remaining + ' more item' + (remaining > 1 ? 's' : ''));
}
}
var syms = typeof gOPS === 'function' ? gOPS(obj) : [];
var symMap;
Expand Down
1 change: 1 addition & 0 deletions readme.markdown
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ Return a string `s` with the string representation of `obj` up to a depth of `op
Additional options:
- `quoteStyle`: must be "single" or "double", if present. Default `'single'` for strings, `'double'` for HTML elements.
- `maxStringLength`: must be `0`, a positive integer, `Infinity`, or `null`, if present. Default `Infinity`.
- `maxArrayLength`: must be a non-negative integer, `Infinity`, or `null`, if present. Default `Infinity`. Specifies the maximum number of elements to include when formatting Arrays, TypedArrays, arguments objects, Sets, and Maps. Elements beyond this limit will be replaced with `... N more items`.
- `customInspect`: When `true`, a custom inspect method function will be invoked (either undere the `util.inspect.custom` symbol, or the `inspect` property). When the string `'symbol'`, only the symbol method will be invoked. Default `true`.
- `indent`: must be "\t", `null`, or a positive integer. Default `null`.
- `numericSeparator`: must be a boolean, if present. Default `false`. If `true`, all numbers will be printed with numeric separators (eg, `1234.5678` will be printed as `'1_234.567_8'`)
Expand Down
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