Count number of tracks in playlists

gistfile1.js

_ = sp.require('underscore');

sp.core.library.getTracks().length

// Versus:

// Total number of tracks in "library" = all playlists
_.reduce(sp.core.library.getPlaylists(), function (a, x) { return a + _.reject(_.map(_.range(x.length || 0), function (i) { return x.getTrack(i); }), function (t) { return t.isLocal || t.isAd || t.isPlaceholder || !t.availableForPlayback; }).length; }, 0)

// Number of unique tracks (unique track URIs)
_(sp.core.library.getPlaylists()).chain().map(function (p) { return _.map(_.range(p.length || 0), function (i) { return p.getTrack(i) }) }).flatten().filter(function (t) { return t.availableForPlayback && !t.isLocal }).map(function (t) { return t.uri }).uniq().size().value()