Exercises 3/7 and 4/7 put calculation inside render function or before creating component class?

[royracer]

In the exercise, 3/7: Put Logic in a Render Function, the lesson says “A render function can also be a fine place to put simple calculations that need to happen right before a component renders. Here’s an example of some calculations inside of a render function”. A “simple calculation” is placed inside the render function:
var n = Math.floor(Math.random()*10+1);

However, in the very next exercise 4/7: Use a Conditional in a Render Function, a very similar calculation is done outside (and before) the call to create the component class:
var fiftyFifty = Math.random() < 0.5;

• When would one want to include such a calculation inside the render function (as in 3/7)?
• When would one want to include it before (as in 4/7)?
• Is one or the other a best practice?

The two exercises seem contradictory or at least don’t explain why to do it one way or the other.

Thanks in advance!
Roy

[mtf]

Is one or the other a best practice?

What defines best practice, in this case? Readability? Caching for re-use? This (4/7) example could be done either way, but given there is some control flow logic, the cached value is more readable.