Tag: javascript

Web performance review: TradeMe

Most of the English-speaking world has Amazon and eBay. In New Zealand we have TradeMe - an online auction & classified advert website where Kiwis go to buy & sell general items, cars, and property. If the numbers are to be believed, then pretty much every Kiwi has a TradeMe account. I don’t think it’s an understatement to say that TradeMe is an itegral part of modern New Zealand culture.

Back in 2016, TradeMe announced that it was working on a new “smartphone-optimised” responsive website that will eventually also replace the desktop website. Then halfway through 2018, they announced that the new responsive website was being rolled out to real users.

Being the ever-curious developer, I wanted to give the new TradeMe website a try. After a couple of weeks using the new website on my phone (a Nokia 7 Plus), I became frustrated with how much time I spent staring at a loading spinner, and how sluggish the UI interactions were. So I went back to the old website.

This bothered me, because I know that the other TradeMe experiences are fast. Why should this new website be so slow? I wanted to dig deeper, so I’ve taken the opportunity to conduct a detailed performance review.

JavaScript Performance: Variable Initialization

Initializing variables properly in JavaScript can have significant performance benefits. This can be shown with a simple synthetic benchmark.

notype.js

var x = null;

for (var i = 0; i < 1e8; i++) {
    x = 1 + x;
}

withtype.js

var x = 0;

for (var i = 0; i < 1e8; i++) {
    x = 1 + x;
}

Understanding JavaScript: Inheritance and the prototype chain

This is the first post in a series on JavaScript. In this post I’m going to explain how JavaScript’s prototype chain works, and how you can use it to achieve inheritance.

First, it’s important to understand that while JavaScript is an object-oriented language, it is prototype-based and does not implement a traditional class system. Keep in mind that when I mention a class in this post, I am simply referring to JavaScript objects and the prototype chain – more on this in a bit.

Almost everything in JavaScript is an object, which you can think of as sort of like associative arrays - objects contain named properties which can be accessed with obj.propName or obj['propName']. Each object has an internal property called prototype, which links to another object. The prototype object has a prototype object of its own, and so on – this is referred to as the prototype chain. If you follow an object’s prototype chain, you will eventually reach the core Object prototype whose prototype is null, signalling the end of the chain.