I disagree. The obvious benefits of Javascript in the browser are that it is distributed universally, can be deployed to others easily, and has a reasonably powerful API (but not powerful enough to shoot your foot). I think the ease of applying the code to real projects can provide an extra amount of motivation to a lot of people who may have no interest in learning either some toy playground or the console.
Remember, the introductory programming class is all about teaching students to talk to their computers in a methoidcal, step-by-step fashion. It's not about the finer points of language design.
> The obvious benefits of Javascript in the browser are that it is distributed universally
Pretty much any open-source language is available on all platforms. Besides, you still need to setup an editor, so it's not like you can skip the whole "install software"-step.
> can be deployed to others easily
In the beginning this doesn't actually matter too much. Beginners are usually aware that they're not creating something that all their friends are going to use, and it's often better to show it to them face-to-face so you can explain things. Sharing code with other students on the other hand is very useful, but JavaScript isn't any different here ("look at my .html" vs "look at my .py").
> a reasonably powerful API (but not powerful enough to shoot your foot)
JavaScript has few built-in libraries, and the DOM API is very HTML-specific and a horrible mess. I don't quite see how these APIs make the students become better programmers; just understand the quirks of HTML more detailed.
1. I'm a little confused why you would object to JavaScript as a first language. You're using it to teach very basic concepts like variables and conditionals. Who cares about polymorphism at that stage?
2. Creating a Web App to follow programming concepts is something John Resig knows how to do. Check out his Advanced JavaScript page for examples:
3. No installation needed. No one has to have permissions to install or modify software or the OS. That's a huge hurdle. If you're at a public library or borrowing your brother's computer, you don't have to worry about permissions, settings, downloads, etc. You're already setup to start with just learning.
Obviously, to become a better programmer you have to learn some more languages, but JavaScript is not going anywhere anytime soon. In fact, there is a higher demand for JavaScript programmers than ever. Why not learn it?
Remember, the introductory programming class is all about teaching students to talk to their computers in a methoidcal, step-by-step fashion. It's not about the finer points of language design.