API · Select

`where()`

Keep objects whose listed properties strictly equal the requested values.

Signature

where(properties: Partial<T>): Exstream<T, C>

Example

const openItalian = exstream(orders).where({ country: 'IT', status: 'open' })

Parameters

properties

Type Partial<T>Required

All enumerable string properties visited by for…in must match with ===. Symbol properties are not checked; inherited enumerable matcher properties are.

Matching

Comparison is shallow. Objects and arrays match by identity, NaN never matches itself, and a missing property can match an explicitly requested undefined. An empty matcher keeps every successful value.

where() is a synchronous filter(): it preserves order and context, adds no queue, and propagates pressure. Existing record errors pass through without matching.

Errors

Reading a property from null or undefined, or from a throwing getter, becomes a filter() record error. Other primitives use normal JavaScript property access.

Forms

stream.where({ status: 'open' })
exstream.pipeline().where({ status: 'open' })
exstream.where({ status: 'open' }, stream)
stream.through(exstream.where({ status: 'open' }))

findWhere(), filter(), pick()

where()