E4X: ECMAScript for XML

E4X gives you the ability to process XML data very elegantly in languages like JavaScript. Here's an example:

var pets =
<pets>
  <domestic>
    <pet animal="dog"><name>Jasper</name><age>13</age></pet>
    <pet animal="cat"><name>Rupert</name><age>12</age></pet>
    <pet animal="cat"><name>Monty</name><age>15</age></pet>
    <pet animal="cat"><name>Tiger</name><age>20</age></pet>
  </domestic>
</pets>

header('-type', 'text/plain');

var cats = pets.domestic.pet.(@animal=='cat');
write('There are ' + cats.length() + ' cats');
write('\n'); // newline

var monty = pets.domestic.pet.(name.toLowerCase()=="monty");
write('Monty is ' + monty.age + ' years old');
write('\n'); // newline

var tiger = pets.domestic.pet[3];
write('Tiger is ' + tiger.age + ' years old');

Here you can see how it's possible to declare XML in JavaScript and select elements using attribute, content and list selectors. To turn any text into an XML object to be processed like this, just use the form var xml = new XML(text); - it really is that simple!