The Author – Bart Busschots
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Sep
29
In the previous instalments we experimented with jQuery using the web console on our dummy page. In this instalment we’ll learn how to embed JavaScript into web pages, and, how to attach our code so it gets triggered by browser events.
This instalment includes a number of examples. You can copy-and-paste the code out of the page, but for convenience I’ve zipped up all the files and you can download them here.
Sep
15
PBS 21 of X – jQuery Basics
Filed Under Computers & Tech, Software Development | 1 Comment
In the previous instalment we took our first tentative steps into the browser. We learned about the Javascript console, the concept of the Document Object Model, or DOM, and we introduced the jQuery library.
Our initial introduction to jQuery was very superficial, now, it’s time to dive in deeper, and get much more rigorous in our understanding. We’ll look at how to use jQuery to select specific HTML elements on the page, and then, how to manipulate their styling, and their HTML attributes.
For this instalment we’ll still be using the Javascript console on the PBS dummy page. From the next instalment on, we’ll be embedding our JavaScript directly into our web pages, so this will be the last time we use the dummy page.
Sep
1
After six instalments, it’s finally time to bring our JavaScript knowledge into the web browser. We’ve already learned that HTML is used to specify the structure of a web page, and CSS to specify its appearance, so where does JavaScript come in? JavaScript’s primary use on the web is to add interactivity and/or automation of some kind. For example, clicking on something could cause the page to change in some way, or, icons could be automatically injected into the page to mark links that open in new tabs as being different to other links.
A key point to note is that HTML, CSS, and JavaScript are all so-called client-side technologies. It’s the web browser doing the work, not the web server. The web server simply delivers the HTML, CSS, and JavaScript code to the browser as text, just like you type it, and the browser then interprets that code and turns it into the web page you see and interact with.
Jul
21
I’m into the second half of my thirties now, and for the last decade or so, my weight had been slowly creeping up. When you’re a teenager, your body seems to be able to burn off enough calories to make up for a bad diet. But, as you get further into your twenties, something happens, and you start to put on weight instead of burning off all those bad-food calories. Eating is something I tend to be very habitual about, so while I made a conscious decision to eat better and exercise more, that never seemed to change anything. I would just continue to eat like I did before, almost as if I was on auto-pilot. I’d find myself eating a Mars bar at 3pm in the afternoon, not because I wanted one, or even because I’d chosen to have one, but because that’s what I’d always done at 3pm, and my body would just move towards the vending machine a that time without any conscious thought at all!
I’d been meaning to tackle my weight for years, but this year, after many false starts, I’m finally succeeding, and the difference with previous failed attempts is technology.
Jul
14
PBS 19 of X – Some JavaScript Challenges
Filed Under Computers & Tech, Software Development | 6 Comments
While recording instalment 18 of the Programming by Stealth series, I promised Allison some challenges to help listeners test and hone their understanding of the core JavaScript language. Since we’ve now covered pretty much the whole language in the series, it’s the perfect time to pause and consolidate that knowledge.
These challenges are designed to be run in the PBS JavaScript Playground. You may also find the PBS JavaScript cheatsheet helpful.
Jul
6
We’ve now covered most of the core JavaScript language. We’ve learned that variables can store literal values, or references to objects. We’ve learned there are three types of literal values – numbers, booleans, and strings. We’ve learned about operators. We’ve learned about conditionals. We’ve learned about loops of various sorts, and we’ve learned about objects. We’ve learned that in JavaScript, arrays are implemented as objects with the prototype Array, and that functions are also implemented as objects.
Before we can leave the playground and head off into the world of the browser, we just have a few more loose ends to tie up, which we’ll take care of in this instalment.
Now that we know about objects, we need to re-visit the arguments object present in every JavaScript function. We need to take a detailed look at the typeof operator, and we need to look at some built-in objects and functions JavaScript provides.
We also need to look at how JavaScript handles regular expressions, and finally, we need to introduce the concept of exception handling.
Jun
23
PBS 17 of X – JS Objects
Filed Under Computers & Tech, System Administration | 4 Comments
At this stage in the series we have made very good progress towards understanding the core JavaScript language. However, there is still one very important piece missing – objects. We have mentioned them in passing in almost every instalment, and each time, we put them off until later. We finally remedy that in this instalment.
Jun
8
PBS 16 of X – JS Callbacks
Filed Under Computers & Tech, Software Development | 1 Comment
In the previous instalment we introduced the concept of JavaScript functions. We learned how to all existing functions, and how to create out own.
In this instalment we’re going to take our understanding of functions to the next level. The techniques we encounter today would be considered advanced techniques in most other languages, and you could spend years developing in Java and never encounter an anonymous function. However, because of how JavaScript is integrated into HTML documents, these techniques are considered fundamental in JavaScript, and anonymous functions are a dime a dozen!
Before we delve into anonymous functions, we’ll start by taking a deeper look at how JavaScript deals with function arguments.
May
27
PBS 15 of X – JS Functions
Filed Under Computers & Tech, Software Development | 1 Comment
At this stage we’ve learned about five key components to any programming language, and how they are implemented in JavaScript – variables, operators, branching, arrays, and loops. Now it’s time to add another – functions.
A function is a collection of statements that is given a name so it can be easily re-used. We’ve already used functions, but without knowing that’s what we’ve been doing.
May
12
At this stage we’ve learned about three of the key components common to just about every programming language, and how they’re implemented in JavaScript – variables, operators, and branching. Now it’s time to add two more – arrays, and loops.
Arrays store a list of related data in a single variable, and loops allow us to apply the same action over and over again. To process an arbitrarily long array, you need some kind of iteration, and loops are the simplest way of achieving that.