Argthtjtr

I’ve just used this expression in the sentences below, and I wonder if the use of it can be somewhat misleading. More specifically, I’m talking about the “to” preceding “fully appreciate”.

I’ve used it to mean “in order to”, but the usual pattern of this expression seems to lead the listener to another interpretation.

“It is one thing to passively learn about ... but to fully appreciate how and when ... is quite another”.

Here, the “to” is used to form a subject noun phrase instead.

What’s your take on this?

“It is one thing to passively learn about all those various commands in JavaScript by poring over online materials. But to fully appreciate how and when to use each one, I need to try them out in my own code and have them corrected by someone in the know.”

’Tis one thing to be tempted, Escalus,
Another thing to fall. (Measure for Measure 2.1.17–18)

The coordinate pairing of infinitives in this construction is so well established that a reader is likely to reach the end of your first sentence waiting for the other shoe to drop. Your then beginning the second with a to infinitive of purpose is thus a kind of garden path. It is grammatically perfectly correct, but not as foolproof for your reader as you can and should make it.

"It is one thing to (blank), but another to (blank)" is a comparative structure.

Taking a cue from your example, it would make more sense to say something like "It is one thing to learn passively, but another to understand the material."

It's used specifically when you're comparing two things, with the second of them being the more important half of the pairing. (Macmillan)

It seems that you want to use unsuccessfully two constructions combined

“It is one thing to passively learn about all those various commands in JavaScript by poring over online materials. However, in order to fully appreciate how and when to use each one, I need to try them out in my own code and have them corrected by someone in the know.”

“It is one thing to passively learn about all those various commands in JavaScript by poring over online materials, but to fully appreciate how and when to use each one, I need to try them out in my own code and have them corrected by someone in the know.”

You are using a shortcut for no particular reason.

First solution is ok. It gives you a rest after one long sentence for approaching another long sentence.

Second one is stressing the importance of the second sentence, you want a reader to concentrate and grasp the complete meaning, compare two choices you are trying to explain. You are building a momentum.

It is up to you which one you like better, but your solution is really neither one nor the other.

It is one thing to X but another to Y

Often means things like:

• 
  X may be good, but Y is much better (or: X may be bad, but Y is much worse)


• Don't mistake X for Y
  


• Don't overestimate X / let X impress you


• Don't underestimate or disregard Y
  

The author of your example sentence implies that although "passively learn[ing] about all of those various commands" may be worthwhile by itself, it can lead you to think you understand more than you really do, and you won't truly understand until you try out all those various commands yourself. In other words, you can't expect to be successful if you only rely on passive learning.

Also, "in order to" is implied in your example sentence. It makes perfect sense when inserted into the sentence:

It is one thing to passively learn about all those various commands ... but in order to fully appreciate how and when to use each one, I need to try them out in my own code.

First, it is always awkward to have anything between to and the infinitive as we were told in grammar school. Secondly, the comparison should form a somewhat sharp contrast rather than two similar but slightly different things. My example is this: "It is one thing for a person to own what he has created; it is another for him to stop others from copying it."