JavaScript types

Explore value categories and their inspection semantics.

Choose the right mental model

A JavaScript value may be a primitive, a collection, an object with identity, or an intentionally opaque value. The inspector chooses a representation for that value directly; it does not serialize the input into JSON first.

Use the type compatibility matrix for the exact display and expansion behavior of each built-in type.

Primitive values retain their meaning

undefined, bigint, symbols, NaN, infinities, and negative zero are distinct values. They are not coerced to JSON-compatible substitutes. Strings are truncated for display according to the inspection string limit; truncation does not modify the original value.

import { DataInspector } from '@nipe-solutions/react-data-inspector'

export function Values() {
  return (
    <DataInspector
      value={{
        missing: undefined,
        identifier: 9007199254740993n,
        label: Symbol('request'),
        numeric: [NaN, Infinity, -0],
      }}
    />
  )
}

Summarized is different from expandable

Date, RegExp, and URL have concise intrinsic summaries. Ordinary objects expose their own properties. Errors expose their own details, including non-enumerable error fields. Arrays and binary values expose indexed children and use grouping when large.

An object summary does not promise that its entire prototype or every host-specific field can be inspected. The matrix states the boundary for each adapter.

Collection addresses are not property paths

Maps can contain object keys. Sets have values without property names. Their rows use explicit iteration-position addresses, so a collection insertion or removal may change what an address refers to.

The inspector does not manufacture JSON Pointers for these rows. See paths for rich addresses and conversion rules.

Opaque values are deliberate

Functions are represented without invocation; Promises are represented without awaiting or reading a resolved state. WeakMap and WeakSet contents cannot be enumerated. Recognized DOM and React values have bounded specialized treatment rather than an unrestricted walk through framework internals.

Opacity is a statement about inspection support, not a claim that a value is empty. Read safe inspection for reflection and custom-callback boundaries.

Teach the inspector about a domain value

A custom type supplies a summary, optional paged children, and optional search text. It composes with either presentation and retains the same navigation, paths, and actions.

Try the predefined JavaScript scenarios. Pasted playground input accepts JSON only; it does not evaluate JavaScript expressions.