This means that for long-running JS applications, like an SPA, JS performance is very good, and in the latest Chrome, it can even improve over time as run-time optimizations are employed.
There are so many what-ifs else's and but's when it comes to benchmarks and performance that it's really hard to know what the answer is. You have to quantify each particular use case, what kind of equipment it will be running on, and then you have to write efficient code in that language. Crap code can be written in any language. Then performance isn't the only reason to choose a language, you have to balance it against ease of use/development/maintenance, how it can interact with other components, how well supported it is in the developer community, and much more before arriving at a conclusion about a technology choice. That's why I say it is "fast enough" because it's to the point where discussions of speed is irrelevant for most applications.