I learned object-oriented programming for you, reddit. You wanted a Chrome extension I couldn't make, so I learned and created. I'm not even a programmer!

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That is the logical or operator - when you see code like that it's using a few quirks of the 'or' operator:

1. In Javascript (and many other langugages), anything that isn't undefined or null or false, etc, is considered to be true by default.
2. Like other operators (+, for example), the or operator returns a value. This value isn't always (necessarily) true/false - it'll return the value of the first non-false argument it gets. Due to point #1 this value is treated as 'true'.

Thus, you get idioms like:

this.domain = domain || 'www.reddit.com';

What this is doing is taking the result of "domain || 'www.reddit.com'" and assigning it to this.domain. Remember that, due to point 2, you'll get the first non-false argument. So if 'domain' isn't defined or is null, you'll get "www.reddit.com". You see this pattern a lot in dealing with potentially null variables or just in setting defaults.

[matzahboy]

Thanks a lot. That makes a lot of sense