Gets the ID of the underlying operation.
import Batch = require("nativescript-batch");
var b = Batch.newBatch(function(ctx) {
console.log("ID: " + ctx.id); // operation-1
});
b.id = "operation-1";
b = b.then(function(ctx) {
console.log("ID: " + ctx.id); // operation-2
});
b.id = "operation-2";
b.start();