code

Maximize JS

JavaScript source maps are really cool. They allow people to ship minified code while retaining the ability to map back to the original source code in development tools like browser debuggers. There are three pieces to a full source map experience when debugging in browsers:

  • The minified script, which the browser has already
  • The source map, which the browser can get from a comment at the end of the minified script
  • The original script, which the browser can get from the source map

The source map and original script are also retrieved from the web server. If you are missing either the source map or the original script, existing tools give up and only show the minified script. I had a theory that the source map contained enough data by itself to make a decent reproduction of the original script. Comments will be missing, whitespace won’t be the same, etc. However, the code would very readable, and details such as what libraries have been used should be evident.

I decided to test the theory by making Maximize. Maximize takes a URL to a script hosted on a website and outputs a deobfuscated, beautified version of the script, assuming the source map is available. For example, this is the beginning of the minified script on fontdragr.com:

"use strict";(function(e,n,t){function r(e){return String.fromCharCode(e)}function i(e){return e&&"number"==typeof e.length?"function"!=typeof e.hasOwnProperty&&"function"!=typeof e.constructor?!0:e instanceof an||Yt&&e instanceof Yt||"[object Object]"!==er.call(e)||"function"==typeof e.callee:!1}function o(e,n,t){var r;if(e)if(k(e))for(r in e)"prototype"!=r&&"length"!=r&&"name"!=r&&e.hasOwnProperty(r)&&n.call(t,e[r],r);

After maximizing, the maximized script starts to look like:

"use strict";
(function(window, document, undefined) {
    function fromCharCode(code) {
        return String.fromCharCode(code)
    }

    function isArrayLike(obj) {
        return obj && "number" == typeof obj.length ? "function" != typeof obj.hasOwnProperty && "function" != typeof obj.constructor ? !0 : obj instanceof JQLite || jQuery && obj instanceof jQuery || "[object Object]" !== toString.call(obj) || "function" == typeof obj.callee : !1
    }

    function forEach(obj, iterator, context) {
        var key;
        if (obj)
            if (isFunction(obj))
                for (key in obj) "prototype" != key && "length" != key && "name" != key && obj.hasOwnProperty(key) && iterator.call(context, obj[key], key);
            else if (obj.forEach && obj.forEach !== forEach) obj.forEach(iterator, context);
        else if (isArrayLike(obj))
            for (key = 0; obj.length > key; r++) iterator.call(context, obj[key], key);
        else
            for (key in obj) obj.hasOwnProperty(key) && iterator.call(context, obj[key], key);
        return obj
    }
...

If you look further into the script, you’ll find the AngularJS¬†library along with all the fontdragr modules and controllers. This is all generated from the minified script and the source map, without any need of the original script! For web developers who minify their scripts partly for obfuscation, watch out!

Standard
From http://bl.ocks.org/mbostock/4060366

How to grab SVGs from websites

So you come across an SVG on a website, and you want to save it to a file. Maybe you want to send it by email, or put it in a presentation, etc. You think, “I know, I’ll just right-click on it and Save as…” Wrong! This saves the webpage itself. In fact, there is no easy way to do this. You can find plenty of people online who also want this functionality, but I haven’t found any solutions that render directly to an svg. I’ve found solutions that render to a PDF, but there are limitations and issues with PDFs. Besides, once you have a real SVG, you can then use other tools to convert it to whatever format you want very easily.

What to do… Well, I spent some time poking around with SVG files and D3 SVG visualizations to figure out how they compared. I noticed that the structure of the HTML <svg> tag and its descendents looked the same as the structure of the SVG element in SVG files. The only difference is that the SVG element in SVG files included two XML namespace attributes as well:

<svg xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" width="620" height="90">

That’s a pretty simple fix, but it’s not quite enough. Now, we need to add a proper doctype header:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

We’re almost there! If you then put these two pieces together in a new file, your SVG may look correct. If your SVG is a D3 visualization, probably not. D3 SVGs use CSS style rules to specify how SVG elements look. Luckily, HTML and SVG use the same CSS mechanism. We simply need to insert all the relevant CSS rules in a new <style> tag under the <svg> tag.

Ok, great, but this is a bit tedious… Yeah, I know, so I wrote¬†svgrab. It’s a node.js script, so install node and npm. Then install the script: npm install -g svgrab. Now you can grab export SVGs from websites to a file like a pro! You can also define a timeout to wait for, since some D3 visualizations are time-dependent. Under the covers, svgrab runs phantomjs, which renders the website in a headless environment. It then selects the first SVG element (you can optionally specify another SVG element if you need) and performs the transformations above.

Now when you need to share your awesome D3 visualization somewhere other than in a browser, you can render to SVG (and then to something else if needed) much easier!

Standard