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As many of us know, IE7 is not quite friendly with JavaScript code containing trailing commas, which can be a large problem for projects using modern JS framerworks and containing a lot of JS code. In a pretty good article on the subject, the author mentions:
On the tools front, my preference for combating these devils is the Eclipse JavaScript Development Tools. The JavaScript source editor in JSDT flags trailing commas as errors: http://www.enterprisedojo.com/wp-content/uploads/2010/12/jsdtRules.png
However, using Eclipse Indigo with WTP/JSDT, I'm not seeing trailing commas as errors, and I can't find a proper setting to fix this.
How do I setup Eclipse to flag trailing commas in JavaScript as errors?
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JavaScript has allowed trailing commas in array literals since the beginning. Trailing commas are now also allowed in object literals, function parameters, named imports, named exports, and more.
A trailing comma, also known as a dangling or terminal comma, is a comma symbol that is typed after the last item of a list of elements. Since the introduction of the JavaScript language, trailing commas have been legal in array literals. Later, object literals joined arrays.
The comma operator in JavaScript is really very simple and, to be 100% honest, you never need to use it.
Require or disallow trailing commas. 🛠Some problems reported by this rule are automatically fixable by the --fix command line option.
It looks like the fix for another bug involving erroneous syntax errors on the comma operator also removed the syntax error on trailing commas in initializers. That's technically correct; the standard says they're allowed and IE7 is just nonconformant. There's a feature request open asking that they be reinstated.
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Slightly off topic, but you should also look into using JSLint to check the syntax of the JavaScript code. It will warn you about the trailing comma, but also about many other potential problems. There is a good plugin for Eclipse, http://marketplace.eclipse.org/content/phonegap-android-jslintjshint. The instructions for setting it up: http://www.mobiledevelopersolutions.com/home/announce-1/mds12released-nowwithjslintjshint
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