for(x=0;x++<50;)console.log((x%3?"":"fizz")+(x%5?"":"buzz"))
Comma-separated, so outputs "fizz buzz" and not "fizzbuzz"
for(x=0;x++<50;)console.log(x%3?"":"fizz",x%5?"":"buzz")
This one is even shorter and outputs numbers instead of blank spaces for fizz and buzz.
for(x=0;x++<50;)console.log((x%3||"fizz")+(x%5||"buzz"))
Or...
for(x=0;x++<50;)console.log(x%3||"fizz",x%5||"buzz")