Inspect JS

Get the byte length of an ArrayBuffer, even in engines without a `.byteLength` method.

Which regular expression flags does the current environment support?

Returns an array of Typed Array names that are available in the current environment

Get the ArrayBuffer out of a DataView, robustly.

Get the byteLength out of a DataView, robustly.

Get the byteOffset out of a DataView, robustly.

`deep-equal`, but only for JSON-supported values.

Does this JS environment support the `name` property on functions?

Gets the description of a Symbol. Handles `Symbol()` vs `Symbol('')` properly when possible.

Does the current environment have `import()` support?

Does the current node version have support for the "exports" field in package.json?

Does the environment have full property descriptor support? Handles IE 8's broken defineProperty/gOPD.

Does this environment have the ability to get the [[Prototype]] of an object on creation with `__proto__`?

Determine if the JS environment has `Symbol.toStringTag` support. Supports spec, or shams.

A robust, ES3 compatible, "has own property" predicate.

Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.

Is this value a JS ArrayBuffer?

Is this value an ES BigInt?

Is this specifier a node.js core module?

Returns true if a value has the characteristics of a valid JavaScript data descriptor.

Is this value a JS DataView? This module works cross-realm/iframe, does not depend on `instanceof` or mutable properties, and despite ES6 Symbol.toStringTag.

Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.

Is this value a JS FinalizationRegistry? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Is this value a JS Map? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Is this value a JS Set? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Is this value a JS SharedArrayBuffer?

Is this value a JS WeakMap? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Is this value a JS WeakRef? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Is this value a JS WeakSet? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Info about node `exports` field support: version ranges, categories, etc.

Determine if the current node version supports the `--preserve-symlinks` flag.

Get the ArrayBuffer out of a TypedArray, robustly.

Robustly get the byte length of a Typed Array

Robustly get the byte offset of a Typed Array

Robustly get the length of a Typed Array

Which kind of boxed JS primitive is this?

What is the type of this builtin JS value?

Which kind of Collection (Map, Set, WeakMap, WeakSet) is this JavaScript value? Works cross-realm, without `instanceof`, and despite Symbol.toStringTag.

node's assert.deepEqual algorithm

return whether two buffers are equal

return the first argument that is `!== undefined`

Determine if the JS environment has Symbol support. Supports spec, or shams.

Determine if the JS environment has template literal support.

Is this an arguments object? It's a harder question than you think.

Determine if a function is a native async function.

Is this value a JS Boolean? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Is this JS value callable? Works with Functions and GeneratorFunctions, despite ES6 @@toStringTag.

Is this value a JS Date object? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Determine if a function is a native generator function.

Is this value negative zero? === will lie to you

Is this value a JS Number object? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Checks whether a value is an object

Is this value a JS regex? Works cross-realm/iframe, and despite ES6 @@toStringTag

Is this value a JS String object or primitive? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Determine if a value is an ES6 Symbol or not.

Is this value a JS Typed Array? This module works cross-realm/iframe, does not depend on `instanceof` or mutable properties, and despite ES6 Symbol.toStringTag.

string representations of objects in node and the browser

Which kind of Typed Array is this JavaScript value? Works cross-realm, without `instanceof`, and despite Symbol.toStringTag.