Better parsing performance on js or php?

Question

PHP

For example, there is html page data + js + css and all this is stored in js objects, which can be tens of thousands.
As a result, you will need to get a large string and push it into a file.
Which big data parsing option will work faster?
1) Process all objects with data in js itself and transfer the already prepared string with ajax to php and get a file from there.
2) Pass all objects in JSON format by Ajax to the php server, and there already get a string from the data and throw it into a file?
As I understand it, parsing will work faster on js, provided that the client has a good computer, there will be trouble on the phone. But there will be stability in php, if all the processing is on the server, then it doesn’t matter what device the client is from, the quality of the server will affect performance. These are just my thoughts, I'm not sure exactly.
Knowledgeable people help with advice.

Answer 1

And why transfer something if everything can be saved to a file on the client?
For example through this