API reference

createBem, BemBlock methods, and validation rules.

createBem(options?)

Creates a frozen BemFactory.

Option	Type	Default	Notes
`namespace`	`string`	`''`	Class prefix; may be empty, no whitespace
`elementSeparator`	`string`	`'__'`	Element separator; non-empty, no whitespace
`modifierSeparator`	`string`	`'--'`	Modifier separator; non-empty, no whitespace

const bem = createBem({ namespace: "acme-" });
const button = bem.block("button");

bem.block(name)

Returns a BemBlock for one block. name must be non-empty without whitespace.

BemBlock methods

Method	Returns
`block()`	`namespace + block`
`element(name)`	block class + element separator + name
`modifier(name)`	block class + modifier separator + name
`elementModifier(element, modifier)`	element class + modifier separator + modifier
`elements(names)`	multiple elements, space-joined
`modifiers(names)`	multiple modifiers, space-joined
`elementModifiers(element, modifiers)`	modifiers for one element
`classes(input)`	conditional mixed output

Batch helpers de-duplicate names stably.

classes(input)

interface ClassInput {
  block?: unknown;
  elements?: Record<string, unknown>;
  modifiers?: Record<string, unknown>;
  elementModifiers?: Record<string, Record<string, unknown>>;
}

truthy → emit, falsy → skip
no implicit parent classes
elements / modifiers / elementModifiers must be non-null, non-array objects

Validation

block / element / modifier: non-empty, no whitespace
namespace: may be '', no whitespace
separators: non-empty, no whitespace
structural mistakes throw TypeError

Names are concatenated as-is; the library does not parse output. Separator characters may appear inside names.

Exported types

BemOptions · BemFactory · BemBlock · ClassInput · Conditions