Parse and serialize Parameter Value Language, a data markup language used by NASA
PVL.js
---
A JS module to parse and serialize Parameter Value Language, a data markup language used by NASA.
#### Parse!
``
> const pvl = require('./pvl/index.js')
> const input = (
ORIGINATING_SYSTEM = "ASTER_FTP";
OBJECT = "FILE_GROUP";
DATA_TYPE = "AST_L1A";
OBJECT = "FILE_SPEC";
FILE_ID = "pg-PR1A0000-2017040601_000_001";
FILE_TYPE = "SCIENCE";
FILE_SIZE = 116503123;
END_OBJECT = "FILE_SPEC";
OBJECT = "FILE_SPEC";
FILE_ID = "pg-BR1A0000-2017040601_000_001";
FILE_TYPE = "BROWSE";
FILE_SIZE = 166428;
END_OBJECT = "FILE_SPEC";
END_OBJECT = "FILE_GROUP")
> const parsed = pvl.pvlToJS(input)
> parsed
PVLRoot {
store: [ [ 'ORIGINATING_SYSTEM', [Object] ], [ 'OBJECT', [Object] ] ],
type: 'ROOT',
depth: 0 }
> JSON.stringify(parsed)
'{"store":[["ORIGINATING_SYSTEM",{"value":"ASTER_FTP","type":"text string"}],["OBJECT",{"store":[["DATA_TYPE",{"value":"AST_L1A","type":"text string"}],["OBJECT",{"store":[["FILE_ID",{"value":"pg-PR1A0000-2017040601_000_001","type":"text string"}],["FILE_TYPE",{"value":"SCIENCE","type":"text string"}],["FILE_SIZE",{"value":116503123,"type":"numeric"}]],"identifier":"FILE_SPEC","type":"OBJECT"}],["OBJECT",{"store":[["FILE_ID",{"value":"pg-BR1A0000-2017040601_000_001","type":"text string"}],["FILE_TYPE",{"value":"BROWSE","type":"text string"}],["FILE_SIZE",{"value":166428,"type":"numeric"}]],"identifier":"FILE_SPEC","type":"OBJECT"}]],"identifier":"FILE_GROUP","type":"OBJECT"}]],"type":"ROOT","depth":0}'
`
#### Serialize!
`
...
> const serialized = pvl.jsToPVL(parsed)
> console.log(serialized)
ORIGINATING_SYSTEM = "ASTER_FTP";
OBJECT = FILE_GROUP;
DATA_TYPE = "AST_L1A";
OBJECT = FILE_SPEC;
FILE_ID = "pg-PR1A0000-2017040601_000_001";
FILE_TYPE = "SCIENCE";
FILE_SIZE = 116503123;
END_OBJECT = FILE_SPEC;
OBJECT = FILE_SPEC;
FILE_ID = "pg-BR1A0000-2017040601_000_001";
FILE_TYPE = "BROWSE";
FILE_SIZE = 166428;
END_OBJECT = FILE_SPEC;
END_OBJECT = FILE_GROUP;
`
#### Traverse the object and get values!
`
...
> parsed.get('ORIGINATING_SYSTEM') // Get the item with the given key
PVLTextString { value: 'ASTER_FTP', type: 'text string' }
> parsed.get('ORIGINATING_SYSTEM').value // Access its value
'ASTER_FTP'
> parsed.getAll('ORIGINATING_SYSTEM') // Since PVL allows duplicate keys
[ PVLTextString { value: 'ASTER_FTP', type: 'text string' } ]
> parsed.aggregates() // Get all OBJECTs and GROUPs
[ PVLObject {
store: [ [Object], [Object], [Object] ],
identifier: 'FILE_GROUP',
type: 'OBJECT' } ]
> parsed.objects() // Get all OBJECTs
[ PVLObject {
store: [ [Object], [Object], [Object] ],
identifier: 'FILE_GROUP',
type: 'OBJECT' } ]
> parsed.objects('FILE_GROUP') // Get all OBJECTs with a given name
[ PVLObject {
store: [ [Object], [Object], [Object] ],
identifier: 'FILE_GROUP',
type: 'OBJECT' } ]
> parsed.aggregates()[0].aggregates()[1].get('FILE_ID').value // Dig deep
'pg-BR1A0000-2017040601_000_001'
`
#### Roll your own!
`
...
> const PVLRoot = pvl.models.PVLRoot
> const PVLTextString = pvl.models.PVLTextString
> const PVLGroup = pvl.models.PVLGroup
> const simple = new PVLRoot().add('FOO', new PVLTextString('BAR')).add('BAZ', new PVLTextString('QUX'))
> simple
PVLRoot {
store: [ [ 'FOO', [Object] ], [ 'BAZ', [Object] ] ],
type: 'ROOT',
depth: 0 }
> console.log(pvl.jsToPVL(simple))
FOO = "BAR";
BAZ = "QUX";
> const complex = new PVLRoot().addAggregate(new PVLGroup('FOO').add('BAR', new PVLTextString('BAZ'))).addAggregate(new PVLGroup('QUX').add('BAR', new PVLTextString('FIZZ')))
> complex
PVLRoot {
store: [ [ 'GROUP', [Object] ], [ 'GROUP', [Object] ] ],
type: 'ROOT',
depth: 0 }
> console.log(pvl.jsToPVL(complex))
GROUP = FOO;
BAR = "BAZ";
END_GROUP = FOO;
GROUP = QUX;
BAR = "FIZZ";
END_GROUP = QUX;
`
Run tests with npm test`.