Ruby Dates to Javascript the Easy Way

Whilst writing the queue management for Cafebop in Javascript using the excellent JQTouch library I came across a problem that I thought would be trivial to solve. In the end it was trivial but maybe it's so trivial that nobody ever mentions it so I couldn't find any info on it.

Basically, I wanted to instantiate a Javascript Date object from a Ruby Date object via a JSON call. The problem is that Javascript's Date object constructor can't parse the default string output by Ruby's Date#to_s.

However, it can parse an integer which is milliseconds since the Unix epoch. Ruby's Date#to_i outputs the number of seconds since the unix epoch. So, using my mad arithmetic skillz, I figured I can create a Javascript Date with:

new Date(rubyGeneratedInteger * 1000);

So my usage of it went something like this. In my rails model, I generate an appropriate integer representation of the timestamp:

	class Order < ActiveRecord::Base
	def queued_at_utc
	queued_at.to_i
	end
	# ...
	end

view raw order.rb hosted with ❤ by GitHub

I make that available to a JSON client through the controller:

	class QueuedOrdersController < ApplicationController
	def show
	respond_to do |format|
	format.json {
	render :json=>@order.to_json(
	:methods=>[:queued_at_utc]
	# ...
	)
	}
	end
	end
	end

view raw queued_orders_controller.rb hosted with ❤ by GitHub

And consume it from the Javascript client thus:

	Date.fromSecondsSinceEpoch = function(seconds) {
	return new Date(seconds * 1000);
	};
	// JSON call to retrieve queued order (using JQuery)
	$.ajax({
	type: 'GET',
	success: handleQueuedOrder,
	url: 'http://localhost:3000/queued_orders/1',
	dataType: 'json'
	});
	function handleQueuedOrder(data) {
	var order = data['queued_order'];
	var queued_at = Date.fromSecondsSinceEpoch(order.queued_at_utc);
	alert('Order queued at: ' + queued_at);
	}

view raw mobile.js hosted with ❤ by GitHub