A very important feature is class-based object orientation, which the vast majority of developers are familiar with, thus it is more natural to use compared to

A very important feature is class-based object orientation, which the vast majority of developers are familiar with, thus it is more natural to use compared to prototype-based OO. Also, tool-visible types allow for better/easier tool-assisted development, something that has been a stumbling block even in the most monstrous of IDEs. For example, ever ctrl-clicked a function assigned to a var in Eclipse?