Edit: in response to "why isn't there a movement around using JavaScript for scientific computing", which I thought was an excellent question (which has crossed my mind on occasion).
Typed arrays and real support for integers are crucial features for scientific computing. Although JavaScript recently got some support for typed arrays, they are pretty awkward to use and there still isn't any support for 64-bit integers, let alone even larger types (128-bit). There's also no support for true multidimensional arrays, meaning you're left to simulate them for yourself like in C. Oh, and let's not forget how awful basic things like equality are in JavaScript. Given how awkward numbers, typed arrays and multidimensional arrays are in JS and how essential all of these things are for scientific computing, I think you can see why this hasn't happened.
You don't have to simulate multidimensional arrays in C. It's just easier than wrapping your head around the weird syntax required to pass them around: http://pastebin.com/JTjQMfxr
Typed arrays and real support for integers are crucial features for scientific computing. Although JavaScript recently got some support for typed arrays, they are pretty awkward to use and there still isn't any support for 64-bit integers, let alone even larger types (128-bit). There's also no support for true multidimensional arrays, meaning you're left to simulate them for yourself like in C. Oh, and let's not forget how awful basic things like equality are in JavaScript. Given how awkward numbers, typed arrays and multidimensional arrays are in JS and how essential all of these things are for scientific computing, I think you can see why this hasn't happened.