Question

I am wondering if a comma trailing an array in javascript is valid?

var settings = {
    'foo'  : oof,
    'bar' : rab,
};

vs

var settings = {
    'foo'  : oof,
    'bar' : rab
};

Note the second example does not have a comma after the last key/value.

Answer 1

Most browsers and implementations do allow a trailing comma, the big BUT is the
“Internet Explorer”.

A trailing comma in most InternetExplorer versions causes BIG trouble. It’ll throw wierd, crazy, strange and unreasonable errors .. you have no idea where you’re at! This is terrible, you’ll fall into deep and serious depressions. The disease also has a name, “evil comma of doom” it was called once.

Conclusion: NEVER.. ever! use a trailing comma in Javascript.