So yeah they optimize for space but they also optimize for execution. For example the closure minifier literally puts everything on one line, without semicolons

So yeah they optimize for space but they also optimize for execution. For example the closure minifier literally puts everything on one line, without semicolons (where possible) and uses commas which forces the JavaScript engine to execute it as a single statement which can be faster. That's just a minor point but it can help with speed. Is it enough of an optimization that it's worth it though? I'm not sure; I haven't seen much in the way of benchmarks in this area.