Abstract operations and other functions drawn from the ECMAScript specification
npm install especially
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ECMAScript Spec Operations, in ECMAScript
Especially has a small-but-growing collection of meta-textual and abstract operations drawn directly from the pages of the ECMAScript 6 draft specification. From common things like Get to dealing with internal slots, Especially has you covered.
Especially has no main module (gasp). Instead, you'll require one of the top-level modules that contain the stuff you want.
- GetIterator: uses the
- IsConstructor: not spec compliant, but the best we can do
- OrdinaryConstruct: use this to get ES6
- Type: returns the types as strings, e.g.
assert: ensures you pass it a boolean, then throws if it's not true
define_built_in_data_property: a shortcut for defining a built-in data property with the usual property descriptor.
- Internal slot management:
make_slots(object, arrayOfSlotNames): call this to initialize an object's internal slots. Often referenced in the spec as "instances of (something) are initially created with the internal slots listed in (some table)."
get_slot(object, name): get the value of an internal slot. Often referenced in the spec as "the value of (object)'s [[SlotName]] internal slot."
set_slot(object, name): set the value of an internal slot. Often referenced in the spec as "Set (object)'s [[SlotName]] internal slot to (a value)."
has_slot(object): check whether an object has an internal slot with the given name. Often referenced in the spec as "If (object) does not have a [[SlotName]] internal slot."
A few well-known symbol are included:
"@@create"will give you a symbol that is used by OrdinaryConstruct and related operations.
"@@iterator"will give you a symbol that is used by GetIterator.
Some of the well-known intrinsic objects are included by name, e.g.
"%ObjectPrototype%". These are used by GetPrototypeFromConstructor and related operations.
Especially is meant to run in Node.js 0.11.9+, at least for now. It uses certain ES6 features so far only implemented in bleeding-edge V8, with the
--harmony flag turned on.
Install it from npm into your project with
npm install especially. And don't forget to run your program, or your tests, with the
You can see examples of it in use in the reference implementation of the ES6 promises specification.