Xah Web Dev Blog Archive 2019-01

2019-04-28

Brendan Eich on Fixing JavaScript String Methods Fail on Emoji

2019-04-27

ECMAScript 2016, 2017, 2018, 2019 new. still incomplete.

2019-04-25

JavaScript requestAnimationFrame sucks

requestAnimationFrame(f): calls the function f when browser is ready to update display.

f is passed a integer ms of type DOMHighResTimeStamp. It is milliseconds from performance.timing.navigationStart.

new Date(performance.timing.navigationStart + ms)

should be equal to

new Date()

let x = performance.now();
let y = performance.timing.navigationStart + x;
let z = new Date();

console.log( new Date(y) )
console.log( z  )

The purpose of requestAnimationFrame is when animation done by JavaScript needs to be updated frequently (say, few times a second). Instead of using setInterval, one can use it in combination with requestAnimationFrame, so that the code runs only when browser updates the display.

Example usage:

const update_clock = ((timestamp) => {
    const dd = new Date(performance.timing.navigationStart + timestamp);
    sec_hand.setAttribute("transform", "rotate(" + (dd.getSeconds()*6 + (dd.getMilliseconds()*6/1000)).toString() +  ")");
});

setInterval( (() => { requestAnimationFrame(update_clock) }) , 1000/20);

SVG Clock

the JavaScript web requestAnimationFrame is nasty. Extremely complex semantics, yet, no loop construct, so that user either need to use recursion with complicated manual timing control, or need to use setInterval anyway.

2019-04-25

Array.prototype.flat (new)

2019-04-22

number faq

Number.prototype.toString

number to string Convert Decimal/Hexadecimal

string to int Number.parseInt

Convert String, Number

2019-04-17

converted all call of Object.getPrototypeOf to Reflect.getPrototypeOf

Reflect.getPrototypeOf

2019-04-13

parceljs, a new js tech. nodejs Ryan Dahl highly recommended. https://parceljs.org

2019-04-10

spent 1 hour on the svg path ellipse. still haven't figured out how to use it to draw a quarter circle arc. extremely idiotic tech.

SVG Path: Elliptical Arc

2019-04-07

HTML4 Frameset, Best Idea Killed by Google

it's a sad story that the html4 frameset is killed, by Google and web dev community beginning around 2005. it's the best idea. Today's html5 and JavaScript still cannot do anything close.

HTML Frameset HTML: Frameset to Split Windows
HTML Iframe HTML: Iframe

Java doc is still (and only one) using frameset https://docs.oracle.com/javase/7/docs/api/

2019-03-24

the JavaScript spec, ECMA-262 ECMAScript® Language Specification (LOL™) is the worst lang spec i've read. It is INCOMPREHENSIBLE and UNNECESSARILY so. Also, originally i put links to it from my tutorial for my own convenience of writing tutorial. But nobody else read it.

2019-03-17

programers posting bullshit to get followers

this guy, posts bullshit daily, for like at least 3 years. basically, it's a marketing strategy, posting drama things and soundbytes to get lots clicks by the masses who don't know stuff. that's at least part of the reason he got 40k followers.

JavaScript here's my intro to the topics he listed

2019-03-05

Google Webfont Tutorial (minor update)

2019-02-26

CSS: user-select

2019-02-23

do you have a specific case situation where programer needs to know type coercion result?

i think when one saw a code location where type coercion is happening, you simply just change the code so it's explicit type conversion, unless it's trivial or well-known cases such as number to string.

type coercion results between types that doesn't make sense, are usually just arbitrary, depending on the lang desiner or what happens to be the case in the lang. especially lang with bad history like js.

2019-02-21

old articles