Tag Archives: JavaScript

Writing regular expressions in the context of a new programming language

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One of the things that is kind of annoying about regular expressions is that every programming language implements them slightly differently. If you can, find someone who can give you the low-down in this new language. Otherwise, you’ll have to stick with googling, which can take a while to figure out what you need. I’ll get you started with a few languages.

General Resources

Two of my favorite and most helpful resources:

  • RegExPlanet.com: lets you test regular expressions in many different languages.
  • Regex Cheat Sheet: has a pretty comprehensive general overview of regex syntax.

Regular Expressions in Ruby

One of the easiest ways to get started with regular expressions in Ruby is via Rubular.com. This site provides a way to test regular expressions against any text, as well as a quick cheat sheet to help. RegExPlanet.com also has a Ruby tester that is in beta.

Regular Expressions in Java

For help with Java, I really like using the tester at RegExPlanet.com. It does two really cool things.

  1. Different Java methods (apparently) use regular expressions differently. RegExPlanet.com shows if and how a regular expression will work with each of the methods.
  2. RegExPlanet.com also provides the ‘Java string’ for use in Java methods. In Java, we have to escape the backslashes with additional backslashes. This can get pretty confusing very quickly, so having RegExPlanet.comgenerate that string for me is very helpful.

Regular Expressions in JavaScript

Using regular expressions in JavaScript was where I really began using the pattern modifiers. If a regular expression is between two forward slashes, pattern modifiers are the letters that come after the last forward slash.

/hello/i

This regular expression will match the word ‘hello’ as well as capitalized ‘Hello’, and all caps ‘HELLO’. It will even match the super fancy ‘hElLo’, if you are into crazy stuff like that. The i modifier tells the regular expression to be case-insensitive.

Another really useful modifier for regular expressions in JavaScript is g, which stands for ‘global’. In JavaScript, regular expressions will find the first time it matches a pattern and then stop. Using the g modifier tells it to find ALL the instances where a string matches the given pattern.

Listening for Events with Backbone Views

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This is something that I’ve learned before, and I think I even have it in my notes from when we first learned this, but on Friday, we used two ways to listen for events in Backbone, and I wanted to really solidify this in my mind so I stop getting confused!

One kind of events we can listen for are browser events like click, hover, or focus. The way to ‘listen’ for these kinds of events in a Backbone View is to use an events property in the Backbone View, like so:

events: { '.delete click': 'removeComment' }

The property of the events object is what event we are looking for. In this example, we are listening for a click action on something with the class ‘delete’. The value of the property is what View property should be called when the event occurs.

The other kind of events we can listen for are Backbone events. These are events like ‘add’, ‘remove’, or ‘change’ in Views, Models, or Collections that can trigger further actions. They are set via the listenTo(); function in the initialize property in the View, like so:

initialize: function (options) { this.listenTo(this.collection, 'add', this.addCommentToWall); }

Here, we are saying that we want this instance of the Backbone View to listen to the instance of a Backbone Collection that has been assigned to it. It is listening for something to be added. When something is added, we want to call addCommentToWall, which is a property of the same instance of the Backbone View.

Recap: I have learned two ways to listen for events using Backbone.js. The events property is for listening for browser events. The listenTo() function in the initialize property is for listening for changes in backbone objects.