To provide logging inside batch operations, you have to define one or more logger callbacks:

import Batch = require("nativescript-batch");

var b = Batch.newBatch(function(ctx) {
    ctx.log("Hello from 1st operation!");
}).then(function(ctx) {
    ctx.log("Hello from second operation!");
});

b.addLogger(function(ctx) {
    console.log("[" + ctx.time + "] " + ctx.message);
});

b.start();