Jorge Mir jorgemir

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

CSS Layout Debugger

A tweet-sized debugger for visualizing your CSS layouts. Outlines every DOM element on your page a random (valid) CSS hex color.

One-line version to paste in your DevTools

Use $$ if your browser aliases it:

~ 108 byte version

OBSOLETE

This entire guide is based on an old version of Homebrew/Node and no longer applies. It was only ever intended to fix a specific error message which has since been fixed. I've kept it here for historical purposes, but it should no longer be used. Homebrew maintainers have fixed things and the options mentioned don't exist and won't work.

I still believe it is better to manually install npm separately since having a generic package manager maintain another package manager is a bad idea, but the instructions below don't explain how to do that.

Fixing npm On Mac OS X for Homebrew Users

Installing node through Homebrew can cause problems with npm for globally installed packages. To fix it quickly, use the solution below. An explanation is also included at the end of this document.

Sans jQuery

Events

// jQuery
$(document).ready(function() {
  // code
})

	(function () {
	var perfBar = function(budget) {

	window.onload = function() {
	window.performance = window.performance \|\| window.mozPerformance \|\| window.msPerformance \|\| window.webkitPerformance \|\| {};


	var timing = window.performance.timing,
	now = new Date().getTime(),
	output, loadTime;

	<!DOCTYPE html>
	<!--[if lt IE 7 ]> <html lang="en" class="ie ie6"> <![endif]-->
	<!--[if IE 7 ]> <html lang="en" class="ie ie7"> <![endif]-->
	<!--[if IE 8 ]> <html lang="en" class="ie ie8"> <![endif]-->
	<!--[if IE 9 ]> <html lang="en" class="ie ie9"> <![endif]-->
	<!--[if (gt IE 9)\|!(IE)]><!--> <html lang="en"> <!--<![endif]-->

	<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

	/*
	* Abstraction.js
	*
	* Copyright (c) 2012 "Cowboy" Ben Alman
	* Licensed under the MIT license.
	* http://benalman.com/about/license/
	*/

	var Abstraction = (function($) {
	var _ = $.prototype;

	$sprites: sprite-map("sprites/*.png");
	$sprites-retina: sprite-map("sprites-retina/*.png");

	@mixin sprite-background($name) {
	background-image: sprite-url($sprites);
	background-position: sprite-position($sprites, $name);
	background-repeat: no-repeat;
	display: block;
	height: image-height(sprite-file($sprites, $name));
	width: image-width(sprite-file($sprites, $name));

	@mixin background-image-retina($file, $type, $width, $height) {
	background-image: url($file + '.' + $type);

	@media (-webkit-min-device-pixel-ratio: 2), (-moz-min-device-pixel-ratio: 2) {
	& {
	background-image: url($file + '@2x.' + $type);
	-webkit-background-size: $width $height;
	}
	}
	}