jackieLin JackieLin

React recently introduced an experimental profiler API. This page gives instructions on how to use this API in a production release of your app.

Table of Contents

Profiling in production
- Create React App
- Webpack 4

Profiling in production

React DOM automatically supports profiling in development mode for v16.5+, but since profiling adds some small additional overhead it is opt-in for production mode. This gist explains how to opt-in.

iOS restrictions re: bringing up the keyboard on programmatic focus

I can't find exact specifications on this, but it seems that iOS restricts bringing up the keyboard via programmatically focusing on <input>. It only brings up the keyboard in response to explicit user interaction.

iOS focus on input field only brings up keyboard when called inside a click handler.
It doesn’t work if the focus is async.

This presents a curious problem when you want to autofocus an input inside a modal or lightbox, since what you generally do is click on a button to bring up the lightbox, and then focus on the input after the lightbox has been opened. Without anything fancy, it actually works ok. The problem shows up when you try to add something fancy like a setTimeout or a promise.then(). I don't know why people would want to use a setTimeout here, but waiting for a promise is actually a pretty common use case. E.g. we try to batch dom manipulations like getting a lightbox to show up inside `requestAnimati

I recently switched over to neovim (see my screenshots at the bottom). Below is my updated config file.

It's currently synchronized with my .vimrc config except for a block of neovim-specific terminal key mappings.

This is still a work in progress (everyone's own config is always a labor of love), but I'm already extremely pleased with how well this is working for me with neovim. While terminal mode isn't enough to make me stop using tmux, it is quite good and I like having it since it simplifies my documentation workflow for yanking terminal output to paste in a markdown buffer.

These days I primarily develop in Go. I'm super thrilled and grateful for fatih/vim-go,

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

Virtual DOM and diffing algorithm

There was a [great article][1] about how react implements it's virtual DOM. There are some really interesting ideas in there but they are deeply buried in the implementation of the React framework.

However, it's possible to implement just the virtual DOM and diff algorithm on it's own as a set of independent modules.

	console.log(1);
	(_ => console.log(2))();
	eval('console.log(3);');
	console.log.call(null, 4);
	console.log.apply(null, [5]);
	new Function('console.log(6)')();
	Reflect.apply(console.log, null, [7])
	Reflect.construct(function(){console.log(8)}, []);
	Function.prototype.apply.call(console.log, null, [9]);
	Function.prototype.call.call(console.log, null, 10);

	function unique_keys(array) {
	var values = {};

	for(var i = 0; i < array.length; i++) {
	values[array[i]] = null;
	}

	return Object.keys(values);
	}

	// Source: https://groups.google.com/forum/#!topic/angular/hVrkvaHGOfc
	// jsFiddle: http://jsfiddle.net/pkozlowski_opensource/PxdSP/14/
	// author: Pawel Kozlowski

	var myApp = angular.module('myApp', []);

	//service style, probably the simplest one
	myApp.service('helloWorldFromService', function() {
	this.sayHello = function() {
	return "Hello, World!"