The JavaScript-mtr Connection, Part 1

1. How to import the mtr-accessor library
2. The structure and contents of the mtr data
3. How to do a basic operation like printing mtr contents to the Max console

Get ready

Using require

autowatch = 1; // Reload the script any time we save new changes
inlets = 1; // One inlet to the js object
outlets = 1; // One outlet from the js object

var mtr = require(“mtr-accessor”);
var myMtr;

function dictionary(v) {
    var d = new Dict(v);
    myMtr = new mtr.Mtr(d, 'dict');
}

The data structure

1. tracks: This holds “track” arrays which in turn hold event info, like event type and event value. Each event type is either a number or an array, making it much easier to handle all of the different possible kinds of inputs from Max!
2. trackInfo: For each track, there is metadata info like track length, whether the track loops, and what speed to playback at.
3. topLevel: This holds any miscellaneous top-level mtr data, like the type of dictionary input that is parsed.
4. isValidInput: This is true if the data was parsed with a supported type, otherwise it is false. isValidInput will be true in our current example because we passed in a supported type (‘dict’) as the second argument to the constructor of mtr.Mtr().

Basic JavaScript access

function postln(v) {
    post(v + '\n');
}

for (var n = 0; n < myMtr.tracks.length; n++) {
    var z = myMtr.tracks[n].length;
    postln("");
    postln("Track " + n);
    postln(" Length: " + myMtr.trackInfo[n].length);
    postln(" Loop: " + myMtr.trackInfo[n].loop);
    postln(" Trackspeed: " + myMtr.trackInfo[n].trackspeed);
    postln("  Event Count: " + z);
    
    // the first and last event info (if available)
    if (z > 0) {
        postln(" First @ " + myMtr.tracks[n][0].accum.toFixed(2) + " ms");
        postln(" Last @ " + myMtr.tracks[n][z-1].accum.toFixed(2) + " ms");
    }
}

Learn More: See all the articles in this series