mqtt-pattern

mqtt-pattern

Fast library for matching MQTT patterns with named wildcards to extract data from topics

Successor to mqtt-regex

Example:

var MQTTPattern = require("mqtt-pattern");

// Wildcards in patterns don't need names
var pattern = "device/+id/+/#data";

var topic = "device/fitbit/heartrate/rate/bpm";

var params = MQTTPattern.exec(pattern, topic);

// params will be
{
	id: "fitbit",
	data: ["rate", "bmp"]
}

var filled = MQTTPattern.fill(pattern, params);
// filled will be
"device/fitbit/undefined/rate/bmp"

MQTTPattern.clean("hello/+param1/world/#param2");
// hello/+/world/#

Installing

With NPM:

npm install --save mqtt-pattern

API

exec(pattern : String, topic : String) : Object | null

Validates that topic fits the pattern and parses out any parameters. If the topic doesn't match, it returns null

matches(pattern : String, topic : String) : Boolean

Validates whether topic fits the pattern. Ignores parameters.

extract(pattern : String, topic : String) : Object

Traverses the pattern and attempts to fetch parameters from the topic. Useful if you know in advance that your topic will be valid and want to extract data. If the topic doesn't match, or the pattern doesn't contain named wildcards, returns an empty object. Do not use this for validation.

fill(pattern : String, params: Object) : String

Reverse of extract, traverse the pattern and fill in params with keys in an object. Missing keys for + params are set to undefined. Missing keys for # params yeid empty strings.

clean(pattern : String) : String

Removes the parameter names from a pattern.

How params work

MQTT defines two types of "wildcards", one for matching a single section of the path (+), and one for zero or more sections of the path (#). Note that the # wildcard must only be used if it's at the end of the topic. This library was inspired by the syntax in the routers for web frameworks.

Examples of topic patterns:

user/+id/#path

This would match paths that start with user/, and then extract the next section as the user id. Then it would get the following paths and turn them into an array for the path param. Here is some input/output that you can expect:

user/bob/status/mood: {id: "bob", path:["status","mood"]
user/bob: {id:"bob", path: []}
user/bob/ishungry: {id: "bob", path: ["ishungry"]

device/+/+/component/+type/#path

Not all wildcards need to be associated with a parameter, and it could be useful to use plain MQTT topics. In this example you might only care about the status of some part of a device, and are willing to ignore a part of the path. Here are some examples of what this might be used with:

device/deviceversion/deviceidhere/component/infrared/status/active: {type:"infrared",path: ["status","active"]}