The Author – Bart Busschots
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Oct
12
PBS 23 of x – Creating Elements with jQuery
Filed Under Software Development, Computers & Tech on October 12, 2016 | 2 Comments
So far in this series we have been using jQuery to alter existing HTML elements by changing their attributes or style. In this instalment we take things to the next level, and learn how to use jQuery to create entirely new HTML elements, and inject them into the DOM, and hence, into the web page.
We’ll be working towards our first truly practical assignment in the series – a function that finds all links on a page, and if, and only if, they lead to an external page, alters them to open in a new tab, and appends an icon indicating that fact. In order to work up to that we need to learn five new things:
- How to build HTML elements with jQuery
- How to inject HTML elements into the DOM
- How to loop through each element represented by a jQuery object
- How to embed images directly into web pages using Data URLs
- How to use the 3rd-party library URI.js to interrogate URLs
There are four examples in this instalment, and a starting-point for the challenge. I’ve gathered them, and the other files they depend on, into a ZIP file which you can download here. It’s assumed that you’ll extract this ZIP file and place the five HTML files and one folder it contains into a folder named pbs23 in your local web server’s htdocs folder. The folder is particularly important because it contains a copy of the URI.js library, and if it’s not in the same folder as pbs23d.html and pbs23-assignment.html, those pages won’t work.
Sep
29
PBS 22 of X – jQuery Events
Filed Under Software Development, Computers & Tech on September 29, 2016 | 3 Comments
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 Software Development, Computers & Tech on September 15, 2016 | 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
PBS 20 of X – JS in the Browser
Filed Under Software Development, Computers & Tech on September 1, 2016 | 4 Comments
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
14
PBS 19 of X – Some JavaScript Challenges
Filed Under Software Development, Computers & Tech on July 14, 2016 | 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
PBS 18 of X – JS Miscellany
Filed Under Software Development, Computers & Tech on July 6, 2016 | 4 Comments
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
8
PBS 16 of X – JS Callbacks
Filed Under Software Development, Computers & Tech on June 8, 2016 | 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 Software Development, Computers & Tech on May 27, 2016 | 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
PBS 14 of X – JS Loops & Arrays
Filed Under Software Development, Computers & Tech on May 12, 2016 | 1 Comment
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.
Apr
9
PBS 13 of X – JS Conditionals
Filed Under Software Development, Computers & Tech on April 9, 2016 | 1 Comment
In the previous instalment we got our first taste of JavaScript. We learned about variables, literal data types, and some basic string and arithmetic operators. In this instalment we’re going to focus on booleans. We’ll look at how non-boolean values get converted to booleans when needed (e.g. is 'boogers' true or false?), we’ll learn about some comparison operators that result in boolean values, and we’ll learn about some logical operators. At that stage we’ll have all the knowledge we need to learn about our third fundamental programming concept – branching.