BFJ

Big-friendly JSON. Asynchronous streaming functions for large JSON data sets.

• Why would I want those?
• What functions does it implement?
• How do I install it?
• How do I use it?
  • bfj.walk (stream, options)
    • Example
  • bfj.parse (stream, options)
    • Example
  • bfj.read (path, options)
    • Example
  • bfj.eventify (data, options)
    • Example
  • bfj.streamify (data, options)
    • Example
  • bfj.stringify (data, options)
    • Example
  • bfj.write (path, data, options)
    • Example
• Is there a change log?
• How do I set up the dev environment?
• What versions of node.js does it support?
• What license is it released under?

Why would I want those?

If you need to parse large JSON strings or stringify large JavaScript data sets, it makes sense to do so asynchronously rather than monopolising the event loop. BFJ implements those asynchronous functions.

What functions does it implement?

Seven functions are exported.

Three are concerned with parsing, or turning JSON strings into JavaScript data:

• walk asynchronously walks a stream, emitting events as it encounters JSON tokens. Analagous to a SAX parser.

• parse asynchronously parses a stream of JSON.

• read asynchronously parses a JSON file from disk.

The four remaining functions handle the reverse transformations; serialising JavaScript data to JSON:

• eventify asynchronously traverses a data structure depth-first, emitting events as it encounters items. By default it coerces promises, buffers, dates and iterables to JSON-friendly values.

• streamify asynchronously serialises data to a stream of JSON.

• stringify asynchronously serialises data to a JSON string.

• write asynchronously serialises data to a JSON file on disk.

How do I install it?

If you're using npm:

npm install bfj --save

Or if you just want the git repo:

git clone git@github.com:philbooth/bfj.git

How do I use it?

Import the library using require:

var bfj = require('bfj');

Seven functions are exported: walk, parse, read, eventify, streamify, stringify and write.

bfj.walk (stream, options)

walk returns an event emitter and asynchronously walks a stream of JSON data, emitting events as it encounters tokens.

It takes two arguments; a readable stream from which the JSON will be read and an options object that supports the following property.

• options.discard: The number of characters to process before discarding them to save memory. The default value is 16384.

The emitted events are defined as public properties of an object, bfj.events:

• bfj.events.array indicates that an array context has been entered by encountering the [ character.

• bfj.events.endArray indicates that an array context has been left by encountering the ] character.

• bfj.events.object indicates that an object context has been entered by encountering the { character.

• bfj.events.endObject indicates that an object context has been left by encountering the } character.

• bfj.events.property indicates that a property has been encountered in an object. The listener will be passed the name of the property as its argument and the next event to be emitted will represent the property's value.

• bfj.events.string indicates that a string has been encountered. The listener will be passed the value as its argument.

• bfj.events.number indicates that a number has been encountered. The listener will be passed the value as its argument.

• bfj.events.literal indicates that a JSON literal (either true, false or null) has been encountered. The listener will be passed the value as its argument.

• bfj.events.error indicates that a syntax error has occurred. The listener will be passed the Error instance as its argument.

• bfj.events.end indicates that the end of the input has been reached and the stream is closed.

Example

var emitter = bfj.walk(fs.createReadStream(path));

emitter.on(bfj.events.array, array);
emitter.on(bfj.events.object, object);
emitter.on(bfj.events.property, property);
emitter.on(bfj.events.string, value);
emitter.on(bfj.events.number, value);
emitter.on(bfj.events.literal, value);
emitter.on(bfj.events.endArray, endScope);
emitter.on(bfj.events.endObject, endScope);
emitter.on(bfj.events.error, error);
emitter.on(bfj.events.end, end);

bfj.parse (stream, options)

parse returns a promise and asynchronously parses a stream of JSON data.

It takes two arguments; a readable stream from which the JSON will be parsed and an options object that supports the following properties.

• options.reviver: Transformation function, invoked depth-first against the parsed data structure. This option is analagous to the reviver parameter for JSON.parse.

• options.discard: The number of characters to process before discarding them to save memory. The default value is 16384.

If there are no syntax errors, the returned promise is resolved with the parsed data. If syntax errors occur, the promise is rejected with the first error.

Example

bfj.parse(fs.createReadStream(path)).
    then(function (data) {
        // :)
    }).
    catch(function (error) {
        // :(
    });

bfj.read (path, options)

read returns a promise and asynchronously parses a JSON file read from disk.

It takes two arguments; the path to the JSON file and an options object that supports the following properties.

• options.reviver: Transformation function, invoked depth-first against the parsed data structure. This option is analagous to the reviver parameter for JSON.parse.

• options.discard: The number of characters to process before discarding them to save memory. The default value is 16384.

If there are no syntax errors, the returned promise is resolved with the parsed data. If syntax errors occur, the promise is rejected with the first error.

Example

bfj.read(path).
    then(function (data) {
        // :)
    }).
    catch(function (error) {
        // :(
    });

bfj.eventify (data, options)

eventify returns an event emitter and asynchronously traverses a data structure depth-first, emitting events as it encounters items. By default it coerces promises, buffers, dates and iterables to JSON-friendly values.

It takes two arguments; the data structure to traverse and an options object that supports the following properties.

• options.promises: By default, promises are coerced to their resolved value. Set this property to ignore if you'd prefer to ignore promises in the data.

• options.buffers: By default, buffers are coerced using their toString method. Set this property to ignore if you'd prefer to ignore buffers in the data.

• options.dates: By default, dates are coerced using their toJSON method. Set this property to ignore if you'd prefer to ignore dates in the data.

• options.maps: By default, maps are coerced to plain objects. Set this property to ignore if you'd prefer to ignore maps in the data.

• options.iterables: By default, other iterables (i.e. not arrays, strings or maps) are coerced to arrays. Set this property to ignore if you'd prefer to ignore other iterables in the data.

The emitted events are defined as public properties of an object, bfj.events:

• bfj.events.array indicates that an array has been encountered.

• bfj.events.endArray indicates that the end of an array has been encountered.

• bfj.events.object indicates that an object has been encountered.

• bfj.events.endObject indicates that the end of an object has been encountered.

• bfj.events.property indicates that a property has been encountered in an object. The listener will be passed the name of the property as its argument and the next event to be emitted will represent the property's value.

• bfj.events.string indicates that a string has been encountered. The listener will be passed the value as its argument.

• bfj.events.number indicates that a number has been encountered. The listener will be passed the value as its argument.

• bfj.events.literal indicates that a JSON literal (either true, false or null) has been encountered. The listener will be passed the value as its argument.

• bfj.events.end indicates that the end of the data has been reached and no further events will be emitted.

Example

var emitter = bfj.eventify(data);

emitter.on(bfj.events.array, array);
emitter.on(bfj.events.object, object);
emitter.on(bfj.events.property, property);
emitter.on(bfj.events.string, string);
emitter.on(bfj.events.number, value);
emitter.on(bfj.events.literal, value);
emitter.on(bfj.events.endArray, endArray);
emitter.on(bfj.events.endObject, endObject);
emitter.on(bfj.events.end, end);

bfj.streamify (data, options)

streamify returns a readable stream and asynchronously serialises a data structure to JSON, pushing the result to the returned stream.

It takes two arguments; the data structure to serialise and an options object that supports the following properties.

• options.space: Indentation string or the number of spaces to indent each nested level by. This option is analagous to the space parameter for JSON.stringify.

• options.promises: By default, promises are coerced to their resolved value. Set this property to ignore if you'd prefer to ignore promises in the data.

• options.buffers: By default, buffers are coerced using their toString method. Set this property to ignore if you'd prefer to ignore buffers in the data.

• options.dates: By default, dates are coerced using their toJSON method. Set this property to ignore if you'd prefer to ignore dates in the data.

• options.maps: By default, maps are coerced to plain objects. Set this property to ignore if you'd prefer to ignore maps in the data.

• options.iterables: By default, other iterables (i.e. not arrays, strings or maps) are coerced to arrays. Set this property to ignore if you'd prefer to ignore other iterables in the data.

Example

var stream = bfj.streamify(data);

stream.on('data', read);
stream.on('end', end);

bfj.stringify (data, options)

stringify returns a promise and asynchronously serialises a data structure to a JSON string. The promise is resolved to the JSON string when serialisation is complete.

It takes two arguments; the data structure to serialise and an options object that supports the following properties.

• options.space: Indentation string or the number of spaces to indent each nested level by. This option is analagous to the space parameter for JSON.stringify.

• options.promises: By default, promises are coerced to their resolved value. Set this property to ignore if you'd prefer to ignore promises in the data.

• options.buffers: By default, buffers are coerced using their toString method. Set this property to ignore if you'd prefer to ignore buffers in the data.

• options.dates: By default, dates are coerced using their toJSON method. Set this property to ignore if you'd prefer to ignore dates in the data.

• options.maps: By default, maps are coerced to plain objects. Set this property to ignore if you'd prefer to ignore maps in the data.

• options.iterables: By default, other iterables (i.e. not arrays, strings or maps) are coerced to arrays. Set this property to ignore if you'd prefer to ignore other iterables in the data.

Example

bfj.stringify(data).
    then(function (json) {
        // :)
    });

bfj.write (path, data, options)

write returns a promise and asynchronously serialises a data structure to a JSON file on disk. The promise is resolved when the file has been written, or rejected with the error if writing failed.

It takes three arguments; the path to the JSON file, the data structure to serialise and an options object that supports the following properties.

• options.space: Indentation string or the number of spaces to indent each nested level by. This option is analagous to the space parameter for JSON.stringify.

• options.promises: By default, promises are coerced to their resolved value. Set this property to ignore if you'd prefer to ignore promises in the data.

• options.buffers: By default, buffers are coerced using their toString method. Set this property to ignore if you'd prefer to ignore buffers in the data.

• options.dates: By default, dates are coerced using their toJSON method. Set this property to ignore if you'd prefer to ignore dates in the data.

• options.maps: By default, maps are coerced to plain objects. Set this property to ignore if you'd prefer to ignore maps in the data.

• options.iterables: By default, other iterables (i.e. not arrays, strings or maps) are coerced to arrays. Set this property to ignore if you'd prefer to ignore other iterables in the data.

Example

bfj.write(path, data).
    then(function () {
        // :)
    }).
    catch(function (error) {
        // :(
    });

Is there a change log?

Yes.

How do I set up the dev environment?

The development environment relies on node.js, JSHint, Mocha, Chai, Mockery and Spooks. Assuming that you already have node and NPM set up, you just need to run npm install to install all of the dependencies as listed in package.json.

You can lint the code with the command npm run lint.

You can run the tests with the command npm test.

What versions of node.js does it support?

0.12 and the latest stable io.js.

What license is it released under?

MIT.