Any JavaScript primitive or Object.
Optional showHidden: booleanOptional depth: numberOptional color: booleanOptional options: "util".InspectOptionsThe util.inspect() method returns a string representation of object that is
intended for debugging. The output of util.inspect may change at any time
and should not be depended upon programmatically. Additional options may be
passed that alter the result.util.inspect() will use the constructor's name and/or @@toStringTag to make
an identifiable tag for an inspected value.
class Foo {
get [Symbol.toStringTag]() {
return 'bar';
}
}
class Bar {}
const baz = Object.create(null, { [Symbol.toStringTag]: { value: 'foo' } });
util.inspect(new Foo()); // 'Foo [bar] {}'
util.inspect(new Bar()); // 'Bar {}'
util.inspect(baz); // '[foo] {}'
Circular references point to their anchor by using a reference index:
const { inspect } = require('util');
const obj = {};
obj.a = [obj];
obj.b = {};
obj.b.inner = obj.b;
obj.b.obj = obj;
console.log(inspect(obj));
// <ref *1> {
// a: [ [Circular *1] ],
// b: <ref *2> { inner: [Circular *2], obj: [Circular *1] }
// }
The following example inspects all properties of the util object:
const util = require('util');
console.log(util.inspect(util, { showHidden: true, depth: null }));
The following example highlights the effect of the compact option:
const util = require('util');
const o = {
a: [1, 2, [[
'Lorem ipsum dolor sit amet,\nconsectetur adipiscing elit, sed do ' +
'eiusmod \ntempor incididunt ut labore et dolore magna aliqua.',
'test',
'foo']], 4],
b: new Map([['za', 1], ['zb', 'test']])
};
console.log(util.inspect(o, { compact: true, depth: 5, breakLength: 80 }));
// { a:
// [ 1,
// 2,
// [ [ 'Lorem ipsum dolor sit amet,\nconsectetur [...]', // A long line
// 'test',
// 'foo' ] ],
// 4 ],
// b: Map(2) { 'za' => 1, 'zb' => 'test' } }
// Setting `compact` to false or an integer creates more reader friendly output.
console.log(util.inspect(o, { compact: false, depth: 5, breakLength: 80 }));
// {
// a: [
// 1,
// 2,
// [
// [
// 'Lorem ipsum dolor sit amet,\n' +
// 'consectetur adipiscing elit, sed do eiusmod \n' +
// 'tempor incididunt ut labore et dolore magna aliqua.',
// 'test',
// 'foo'
// ]
// ],
// 4
// ],
// b: Map(2) {
// 'za' => 1,
// 'zb' => 'test'
// }
// }
// Setting `breakLength` to e.g. 150 will print the "Lorem ipsum" text in a
// single line.
The showHidden option allows WeakMap and
WeakSet entries to be
inspected. If there are more entries than maxArrayLength, there is no
guarantee which entries are displayed. That means retrieving the same WeakSet entries twice may
result in different output. Furthermore, entries
with no remaining strong references may be garbage collected at any time.
const { inspect } = require('util');
const obj = { a: 1 };
const obj2 = { b: 2 };
const weakSet = new WeakSet([obj, obj2]);
console.log(inspect(weakSet, { showHidden: true }));
// WeakSet { { a: 1 }, { b: 2 } }
The sorted option ensures that an object's property insertion order does not
impact the result of util.inspect().
const { inspect } = require('util');
const assert = require('assert');
const o1 = {
b: [2, 3, 1],
a: '`a` comes before `b`',
c: new Set([2, 3, 1])
};
console.log(inspect(o1, { sorted: true }));
// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set(3) { 1, 2, 3 } }
console.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));
// { c: Set(3) { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }
const o2 = {
c: new Set([2, 1, 3]),
a: '`a` comes before `b`',
b: [2, 3, 1]
};
assert.strict.equal(
inspect(o1, { sorted: true }),
inspect(o2, { sorted: true })
);
The numericSeparator option adds an underscore every three digits to all
numbers.
const { inspect } = require('util');
const thousand = 1_000;
const million = 1_000_000;
const bigNumber = 123_456_789n;
const bigDecimal = 1_234.123_45;
console.log(thousand, million, bigNumber, bigDecimal);
// 1_000 1_000_000 123_456_789n 1_234.123_45
util.inspect() is a synchronous method intended for debugging. Its maximum
output length is approximately 128 MB. Inputs that result in longer output will
be truncated.
The representation of object.
Any JavaScript primitive or Object.
Optional showHidden: booleanOptional depth: numberOptional color: booleanOptional options: "util".InspectOptionsGenerated using TypeDoc
The
util.inspect()method returns a string representation ofobjectthat is intended for debugging. The output ofutil.inspectmay change at any time and should not be depended upon programmatically. Additionaloptionsmay be passed that alter the result.util.inspect()will use the constructor's name and/or@@toStringTagto make an identifiable tag for an inspected value.Circular references point to their anchor by using a reference index:
The following example inspects all properties of the
utilobject:The following example highlights the effect of the
compactoption:The
showHiddenoption allowsWeakMapandWeakSetentries to be inspected. If there are more entries thanmaxArrayLength, there is no guarantee which entries are displayed. That means retrieving the sameWeakSetentries twice may result in different output. Furthermore, entries with no remaining strong references may be garbage collected at any time.The
sortedoption ensures that an object's property insertion order does not impact the result ofutil.inspect().The
numericSeparatoroption adds an underscore every three digits to all numbers.util.inspect()is a synchronous method intended for debugging. Its maximum output length is approximately 128 MB. Inputs that result in longer output will be truncated.Returns
The representation of
object.