What's wrong with this javascript? Array not defined

It's not php - you should use

var variable_name = new Array()

or even better

var variable_name = []

That's not how to declare variables as an empty array. You should be using:

var articleHTML = [];

See this previous question for reasoning of using this method instead of new Array()

It's [] in ECMAScript; this isn't PHP. The interpreter is right - array is not defined, which is why you're getting that.