# Introspection

> USearch for JavaScript

```javascript
const { metadata, size, capacity, memoryUsage, cpuClass, gpuClass, shardsCount } = index.describe();
metadata.dimensions;                                   // The frozen geometry, as a checkpoint reports it
const containsKey = index.contains(42n);               // Whether a key is in the index
const count = index.count(42n);                        // The number of vectors under a key
const { audited, reachable } = index.health();        // How much of the graph a search reaches

usearch.version();
usearch.capabilitiesCompiled();
usearch.capabilitiesAvailable();
```

`health` audits from the search landmarks, and entries it misses stay unfound until a `refine` re-links them; its `sweeps` counts the levels the audit took to converge.

`import * as usearch from 'usearch';`

## DenseIndexDescription

A live index's frozen metadata and current counters, each read once.

```typescript
interface DenseIndexDescription
```

- `metadata` `DenseMetadata`: The frozen metric, quantization, dimensions and connectivity, as a checkpoint reports them.
- `size` `number`: Stored entries.
- `capacity` `number`: Entries hosted without growing again.
- `memoryUsage` `number`: Bytes the handle holds; traversal scratch is the executor's.
- `cpuClass` `string`: The CPU class dispatch picked on this machine by its canonical name.
- `gpuClass` `string`: The GPU class dispatch picked on the index's devices; "unknown" for a host index.
- `shardsCount` `number`: Live shards.

## DenseReachability

One reachability audit: the population it judged, and how much of it a search reaches.

```typescript
interface DenseReachability
```

- `audited` `number`: Entries published when the audit started; compare `reachable` against this, never a later size.
- `reachable` `number`: Of those, the entries a search reaches from the landmarks; the rest stay unfound until a [`refine`](https://www.unum.cloud/docs/usearch/javascript/metrics.md#refine).
- `sweeps` `number`: Levels the sweep took to converge.
- `backSweeps` `number`: Levels the sweep back toward the entry point took, where an audit sweeps both ways.

## version

The library's version, as the release tooling stamped it.

```typescript
function version(): string
```

## capabilitiesCompiled

The hardware capabilities this binary was compiled with, comma-separated.

```typescript
function capabilitiesCompiled(): string
```

## capabilitiesAvailable

The hardware capabilities the current machine offers at runtime, comma-separated.

```typescript
function capabilitiesAvailable(): string
```