You don't say how much experience you have, how many hours/day, which city you work in, or in which industry. So I'll answer assuming you're junior but you've been doing this for at least a year, you can write good code and good English, you're working 8 hour days, you're in Sydney or Melbourne, and you contract out to an agency doing work for mid-size companies.
I'd say you are at the very very low end of the scale, if not falling off the scale. If you have any skill in front-end JS, and aren't a trainee or a recent graduate with zero experience, you should be getting twice that money easily.
For a comparison, I do back-end and devops work, and I charge in the range between $85 and $175 per hour (1), depending on the client and the work. Right now I have a project of each. I suspect I'm also undercharging some clients, and that intermediaries who genuinely can't pay me more are also undercharging. However, I don't work for recruiters/outsourcers, but directly for companies shipping software, though some of them are intermediaries in the sense that they run a project for a client, and then hire me as a contractor instead of as an employee. Also, I haven't done almost any front-end work, but it's my impression that front-end skills are in higher demand, and rates are higher on average.
(1) AUD, not USD.
You say you don't have other people's salaries to compare. I too wish Aussie JS and front-end freelancers shared their fees here. Here's how to compare freelance day/hour rates to a full time salary, by the way:
A full time worker puts in about 2000 hours a year. As a freelancer, you have to put in your own training, sales (finding work), you pay your own superannuation (because you do, right?), equipment (you buy your own laptop), training (you buy your own books and courses, you pay your own way to attend conferences), etc.
Thus, when comparing your day rates with the money a full time worker gets, you should take into account extra benefits paid by their employer like super (for non-australians, this is a retirement account, by law employers' contributions are about 9%, but some companies pay more, up to the mid-10s), training courses and conferences, etc.
As a freelancer, you don't have sickies or paid holiday of any kind, so you should account for 1000 billable hours a year. Working more is the cherry on top, and less is a risk that you hedge by having good rates.
Therefore, $85/hour is more or less equivalent to an $85.000/yr salary + benefits. $175/hour would be equivalent to $175.000/year salary + benefits.
Obviously this is without taking into account tax brackets, forced downtime if you have health issues, and the averaging of good and bad weeks/months/years. Also, perceptions of salaries/rates aren't linear, neither for you nor for potential employers.
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Note: this advice is for an hourly rate programmer. HN legends patio11 and tptacek will rightly advise you to get out of this game if you can, and I agree with them. I'm trying to do it myself. But while you're in it, this is what I've learnt that I can share.
http://www.kalzumeus.com/2011/10/28/dont-call-yourself-a-pro...
http://www.kalzumeus.com/2012/09/17/ramit-sethi-and-patrick-...
https://news.ycombinator.com/item?id=6974166
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There is a lot of the above advice that you start applying now while still in the hourly rate game, so I'm pasting the link to tptacek's comment again, because it's hella relevant and pithy.
https://news.ycombinator.com/item?id=6974166
Good luck. And to my fellow Aussie freelancers, please share your rates and help everybody negotiate better with clients and employers.