I have several questions

[MorningSTAR-αΩ]

First off after defeating the Wall of Flesh the Hallow and Crimson get unleashed in a V shape, it is always on the same side or is it random
Secondly regarding the Jungle, is it worth it to pre-emptibly hallow an area between it and the center of the map to prevent the other biome form effecting it, ow would the V overise it anyway?

 

[General Milky]

Random

Generally, it's a waste of time to try and contain the crimruption from the jungle, but in worst case scenario you can holy water and eventually clentaminate the surrounding area to hallow. Your jungle will almost never suffer content-robbing loss, only aesthetic.

 

[piemansauce🌳]

First off after defeating the Wall of Flesh the Hallow and Crimson get unleashed in a V shape, it is always on the same side or is it random
Secondly regarding the Jungle, is it worth it to pre-emptibly hallow an area between it and the center of the map to prevent the other biome form effecting it, ow would the V overise it anyway?

DAT jontron reference XD

You shouldn't ho to the trouble of containing it though

 

[DJFlare84]

Secondly regarding the Jungle, is it worth it to pre-emptibly hallow an area between it and the center of the map to prevent the other biome form effecting it, ow would the V overise it anyway?

The placement of the new strips of hallow and creep (evil biome) would be random. They might start from the center of the map, they might start from a little ways AWAY from the center, or they might make a perfect X across the center of the map, so there's no way to tell where the new strip of creep will be.

All you can do is engage hardmode, take a look at where the strips appeared, and hope that the creep didn't go directly through your jungle.

If the creep didn't go through your jungle, then you can go underground around the edge of it and set up a hallowed barrier around the edge so creep can't sneak back in.

if the crimson DID go through your jungle, you'll want to try and obtain a clentaminator ASAP, and then cleanse that sumb*tch (use GREEN solution). Once cleansed, also do the hallow barrier thing to prevent re-creeping.

For the most part though, the Jungle can mostly take care of itself now as long as there's a lot of chlorophyte around it. Creep simply can't get past an area that has any in it. The only problem you need to worry about is setting up a barrier on the surface since Chlorophyte can't and won't grow, spread OR turn dirt into mud there.

 

[Samrux]

Nothing too bad actually happens if the crimson collides with your jungle. The jungle is huge anyways, and the spreading speed is overrated.

 

[N32Cx48]

Most of the time, the Hallow (In about 50 worlds I've made) LOVES to generate on the left side at the site of Wall of Flesh's death, and the Crimson/Corruption on the other side. Usually, if Crimson or Corruption touches the side of the Jungle, just leave it to be. It takes a long time for them to convert the entire Jungle into their respective biomes, usually (even if I have really bad luck and takes me days to kill the 3 Mech Bosses) the Jungle will still have a large patch that survives the attack after the defeat of Plantera. If they generated in the middle of the Jungle, you can either leave it to be, or try to save it using Clentaminator. In my gameplay so far I've not used the Clentaminator except to spread the Hallow as it almost always generates in my Jungle, The Crimson/Corruption usually are still far from taking over the Jungle when I've finally defeated Plantera. (Usually takes a few weeks of Terraria Days!)