Remember my details

I have added JavaScript to the upload form Picky Picky Game on caption.org to optionally remember your details for next time (using a cookie). This way you don’t have to enter your URL each time you upload a new panel.

Debugging JavaScript without a JavaScript debugger is a real pain in the arse, and illustrates how subtle aspects of language design affect the experience of working in that language. There is one crucial difference between Python and JavaScript. In Python, a variable is implicitly created the first time you assign to it; in JavaScript, it is created the first time you refer to it. This means that the following fragment is valid JavaScript:

var cookieHeader = this.$document.cookie;
var m = myRegexp.exec(cookiesHeader);
if (m) {
    ... use the match info to process the cookies ...
}

The equivalent Python looks like this:

cookieHeader = self._document.cookie
m = myRegexp.search(cookiesHeader)
if m:
    ... use the match info to process the cookies ...

In the JavaScript version, the regexp (used to extract one cookie from the Cookies header) will mysteriously never match and you will spend ages scrutinizing the regexp and flipping though the documentation on what is and is not valid regexp syntax in JavaScript. In Python you will get an error message telling you that the variable cookiesHeader is referred to before it is assigned to—and immediately realise its name is misspelled in the second line.

The tedious thing about testing the ‘remember me’ option is that it involves repeatedly doing the very thing it is supposed to be saving me from: entering my URL and details on the picture-upload form. Luckily I was testing on Safari, which has a form auto-completion feature that makes repeatedly filling in the form less annoying—but which also makes the ‘Remember me’ feature almost entirely redundant ;-)