EMA JS Parser

A Generic parser for Enhancing Music Notation Addressability (EMA) expressions (read the API specification here)

This parser is format agnostic, but requires some information about the document to which the EMA expression applies. These data must be structured according to the information request documented in the API. For example:

{
  "measures": 4,
  "staves": {"0": ["Soprano", "Alto", "Tenor", "Bass"] },
  "beats": {"0": {
    "count": 4,
    "unit": 4
  }}
}

Note that measure_labels, and completeness from the EMA spec can be omitted. Stave labels can also be blank, but must be listed:

"staves": {"0" : ["", "", "", ""] },

Building and development

This is a TypeScript library that gets transpiled into JavaScript for use with Node and browsers. You'll need NodeJS and a node package manager installed (we recommend yarn).

To install and test:

yarn install
yarn test

To build JS code:

yarn build

Usage

import * as EmaExp from '../src/EmaExp'

// You can derive document information from an EMA server.
// `GET /{identifier}/info.json`
const docInfo = {
  measures: 4,
  staves: {0 : ['Soprano', 'Alto', 'Tenor', 'Bass'] },
  beats : {0 : {'count': 4, 'unit': 4} }
}

// return an EmaExpr object containing an EmaSelection measure selection with further selections in the object.
const exp = EmaExp.fromString(docInfo, '2-end/start-2/@all/cut')
// return an EmaSelection object containing a staff selection
const m = exp.selection.getMeasure(2)
// return an array of EmaBeatRange containing beat ranges
const s = m.getStaff(1)
// get start of beat range.
s[0].start

Methods are chainable:

exp.selection.getMeasure(2).getStaff(1)[0].start

Beats are returned as a range with range tokens ('start', 'end', and 'all') resolved according to the beat counts provided in the document information JSON.

See tests/test.ts for more examples.