Conditionals with underscore.js

underscore_conditionals.js

// A means of using underscore.js to do templates with conditionals
// Inside of underscore's template, it returns a function that uses
// 'with' on a variable named obj, and you can touch into that using
// inline JS and <% %> wrappers

// A template with conditional display of last names:
var good = _.template("Hello: <%= name %> <% if (obj.lastname) { %> <%= lastname %> <% } %>");

// A template that tries to do that, but fails:
var bad = _.template("Hello: <%= name %> <% if (lastname) { %> <%= lastname %> <% } %>");

// The second approach doesn't fail initially, but will throw a
// 'lastname is not defined' error when you try to use the template.

// It's ugly, but it works.