Question: > 
> Use spaces liberally throughout your code. “When in doubt, space it out.”
> 
> 
> 

In the above sentence, what does "space it out" mean?

Source: <https://make.wordpress.org/core/handbook/best-practices/coding-standards/javascript/#spacing>

Answer: 
In your example

> 
> space it out
> 
> 
> 

means to add spaces (or whitespaces) to make the code easier for humans to read.

Consider the difference between

> 
> def myMethod(a,b,c)if(a==b)t=0;elseif(b==c)t=a;else t=c;end;return t;end
> 
> 
> 

and

> 
> def myMethod(a,b,c)  
> 
>      if(a==b)  
> 
>          t=0;  
> 
>      elseif(b==c)  
> 
>          t=a;  
> 
>      else  
> 
>          t=c;  
> 
>      end;  
> 
>      return t;  
> 
>  end
> 
> 
> 

the nesting, using additional whitespace indentation, more clearly shows how the code will execute given different conditions. In some circumstances, behind the scenes, the additional whitespace is automatically removed (since the computer does not need it) in a process call "minification".

Your example also uses the well known construction since "doubt" and "out" rhyme

> 
> when in doubt, *something* it out
> 
> 
> 

where *something* can be any verb that goes with "out" as long as the context makes sense

> 
> when in doubt, white it out *(with correction fluid)*  
> 
>  when in doubt, scream it out  
> 
>  when in doubt, cut it out *(a possible saying by surgeons)*  
> 
>  when in doubt, ride it out  
> 
>  when in doubt, wait it out 
> 
> 
>
The construction 

> 
> (verb) + **it out**
> 
> 
> 

can be used to emphasize a verb in the sense to do that verb more, to do it until its maximum capacity, or to do it completely.
So your example means

> 
> use more spaces 
> 
> 
> 

In other words, it means exactly what the first part says

> 
> Use spaces liberally throughout your code
> 
> 
> 

There are other examples:

* *Talk it out*  

To talk until you are satisfied, or until you express all your burdensome emotions
* *Work it out*  

To work on a problem until it is finished or fixed
* *Stretch it out*  

To stretch something, like a muscle until it is warmed up, or a rubberband until it is about to break
* [*Stick it out*](http://idioms.thefreedictionary.com/stick+it+out)  

To continue to do something to its end

There are other examples. 

Further, the meaning I gave is not strict. Here is a special case.

> 
> [cut it out](http://idioms.thefreedictionary.com/cut+it+out) 
> 
> 
> 

It means to stop something completely. For example, if you are trying to study, but your little brother or sister keeps asking you to play, you might tell him or her "Cut it out!"