Kira hackergrrl

understanding callbacks & async code flow

Consider setTimeout: a very simple asynchronous function. It takes two parameters: a callback and a delay:

setTimeout(fn, delay)

In use, it might look something like this:

unpackage the board and plug it into your laptop

particle's "getting started" guide:

	#!/usr/bin/env bash

	perf record -e cycles:u -g -- node --perf-basic-prof $1
	perf script > perf-script.txt
	cat perf-script.txt \| flamegraph -t perf > perf-graph.svg
	chromium perf-graph.svg

	#!/usr/bin/env bash

	perf record -e cycles:u -g -- node --perf-basic-prof $1
	perf script > perf-script.txt
	cat perf-script.txt \| flamegraph -t perf > perf-graph.svg
	chromium perf-graph.svg

	#!/usr/bin/env bash

	perf record -e cycles:u -g -- node --perf-basic-prof $1
	perf script > perf-script.txt
	cat perf-script.txt \| flamegraph -t perf > perf-graph.svg
	chromium perf-graph.svg

	function getOsmDocFromVersionId (osmdb, version, done) {
	osmdb.get(version, function (err, node) {
	if (err) done(err)
	else done(null, getOsmDocFromHyperlogNode(node))
	})
	}

	function getOsmDocFromHyperlogNode (node) {
	if (node.value && node.v) return node.value.v // Returns the OSM document (has 'type', 'lat', 'lon', etc)
	if (node.value && node.d) return null // This document is a deletion marker for an older document

	var hyperlog = require('./')
	var level = require('level')
	var through = require('through2')
	var memdb = require('memdb')
	var TopoSort = require('topo-sort');
	var dedupe = require('dedupe')

	if (process.argv.length !== 4) {
	console.error('USAGE: rebuild <LEVEL-DIR> <NEW-LEVEL-DIR>')
	process.exit(1)