Introducing JavaScript

JavaScript has changed a great deal since it was first introduced but many sites still use outdated techniques. There are even lots of JavaScript tutorials on the web that show you how JavaScript should be written so that it can work in Netscape 2 rather than so that it will work in modern browsers. As a result there are many people who are writing what they think is JavaScript but where what they are producing is more suited to the 20th Century than to the 21st.

Beginners should work through all the basic examples prior to moving on to the other examples which cover separate aspects of JavaScript in more detail.

Most of the JavaScript examples here will work in IE5+ (provided you use a deprecated MIME type - otherwise IE9 through 11 only), Opera7+ and all versions of Firefox, Safari, Vivaldi and Chrome. Those commands introduced in ECMAScript5.1 in 2011 have been added (if I have missed any please let me know). Those commands introduced in ECMAScript2015 and ECMAScript2016 are currently being added (there are lots of them for 2015 so it may take some time but then most current browsers do not yet support them all anyway). Where these new commands are not supported by IE8 that information is included in the text - just in case you still have lots of people using that long unsupported browser. So few people using other browsers fail to keep their browser up to date that lack of support in older versions of other browsers should not have any significant affect.

There is a link to jsBin at the bottom right of all the pages. This site provides an easy way to test your JavaScript code online without needing to create an entire web page to run a simple test.

Greedy and Reluctant

One of the issues with pattern matching is where different amounts of text can match the same pattern. Do we want the pattern to match as much of the text as possible or do we want it to match as little as possible so that hopefully more of the text can then also be separately […]

Repetitions

Programs would be extremely awkward to write if it wasn’t possible to create loops within the code so as to repeat the ame code a variable number of times. Regular expressions contain a similar notation for handling repetitions within a pattern so that we can specify the minimum and maximum number of times that particular […]

Character Classes

A character class is a grouping of characters any one of which can validly appear at that spot in the text and match on that part of the regular expression. By grouping characters together into a character class we can specify the pattern in fewer characters than would be needed if we were to include […]

Meta Characters

There are fifteen characters that have a special meaning and which need to be escaped inside an expression where we want the character to have its regular meaning. These fifteen characters are collectively known as meta characters.

Start and End

Now that we have looked at a few of the things that can be done with regular expressions it is time to start looking at the meanings of the codes that can be used within the expressions themselves. The first two special characters we will look at are those which specifically match to the start […]

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