I have written apps in Dart, CoffeeScript, and JavaScript. CoffeeScript is a definite improvement on JavaScript, but I find it still lacks a lot compared to Dart. I still hope Dart takes off, and any new language needs at least 10 years to gain any amount of significant support.<p>I also find that JavaScript developers <i>love</i> their spaghetti code. Bad code proliferates in the JavaScript world. Many may disagree with me, but the empirical evidence does not. Just look at the codebase for any major product, like jQuery for example. I have encountered JavaScript developers with years of experience encourage practice that in any other language would be considered a "hack."<p>Edit: By this, I mean some JavaScript developers will not like Dart because it's too different and restrictive compared with JavaScript.