How To Have A Mob With A BOSS BAR In Minecraft! (Updated Tutorial, 1.16+ (Java))

Made this in Java 1.16.3 (1.16+ should work)
***Let me know if you want a video about boss bars in general
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TIME STAMPS:
0:00 -- Intro
1:12 -- Creating a Bossbar (example)
1:33 -- Stylizing (example)
1:56 -- Tutorial Notes
2:34 -- Making a Mob (example)
3:48 -- Setting the Players (start of health tutorial)
4:25 -- Setting the Max Health
6:02 -- Setting the Health
6:54 -- Visibility Part 1
7:31 -- Visibility Part 2
8:03 -- Notes
8:22 -- Data and "Attributes[?].Base"
9:06 -- Absorption Notes
10:35 -- Health Boost Notes
12:06 -- Conclusion
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COMMANDS:
/gamerule commandBlockOutput false -- do this first!
/give @p minecraft:command_block -- gives normal command block
/give @p minecraft:repeating_command_block -- gives repeating com block
/data get entity @e[(boss identifiers)] -- gets the mob data
1. /bossbar add (bossbar ID) "(bossbar name)" --adds a bossbar
2. Stylize it as you see fit (/bossbar set (bossbar ID) color blue, etc.)
3. Create your mob (how to give it custom health: https://www.youtube.com/watch?v=bcKgEKTWmm8)
4. Set the players (normal or repeating command block):
/bossbar set (bossbar ID) players @a
5. Set the max health OPTIONS:
/bossbar set (bossbar ID) max (value) -- normal command block OR
/execute store result bossbar (bossbar ID) max as @e[(boss identifiers)] run data get entity @s Attributes[0].Base --repeating command block
6. Set the health:
/execute store result bossbar (bossbar ID) value as @e[(boss identifiers)] run data get entity @s Health -- repeating
7. Turning it off:
/execute unless entity @e[(boss identifiers)] run bossbar set (bossbar ID) visible false
8. Turning it on:
/execute if entity @e[(boss identifiers)] run bossbar set (bossbar ID) visible true
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EXAMPLE:
/bossbar add jimbo {"text":"It do be Jimbo Tho"}
/bossbar set jimbo color blue
/summon minecraft:illusioner ~ ~1 ~ {Attributes:[{Name:"minecraft:generic.max_health",Base:400}],Tags:["gop"],Health:400,CustomName:"\"Woaw\"",CustomNameVisible:1,HandItems:[{id:"bow",Count:5}]}
/data get entity @e[type=minecraft:illusioner,limit=1]
/bossbar set jimbo players @a -- repeating
/execute store result bossbar minecraft:jimbo max as @e[type=minecraft:illusioner,limit=1] run data get entity @s Attributes[0].Base --repeating
/execute store result bossbar minecraft:jimbo value as @e[type=minecraft:illusioner,limit=1] run data get entity @s Health -- repeating
/execute unless entity @e[type=minecraft:illusioner,limit=1] run bossbar set minecraft:jimbo visible false --repeating
/execute if entity @e[type=minecraft:illusioner,limit=1] run bossbar set minecraft:jimbo visible true --repeating
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JORG'S EXAMPLE:
/bossbar add jorg {"text":"JORG","color":"light_purple","bold":true}
/bossbar set jorg color purple
/summon husk ~ ~1 ~ {ArmorItems:[{id:"golden_boots",Count:1},{id:"iron_leggings",Count:1},{id:"chainmail_chestplate",Count:1},{id:"player_head",tag:{SkullOwner:"Jorge"},Count:1}],HandItems:[{id:"golden_sword",tag:{Enchantments:[{id:"sharpness",lvl:1},{id:"knockback",lvl:3}]},Count:1},{}],Attributes:[{Name:"minecraft:generic.max_health",Base:69}],Health:69,Tags:["jog"]}
/execute store result bossbar minecraft:jorg max as @e[tag=jog,limit=1] run data get entity @s Attributes[2].Base
/execute store result bossbar minecraft:jorg value as @e[tag=jog,limit=1] run data get entity @s Health
/execute unless entity @e[tag=jog,limit=1] run bossbar set minecraft:jorg visible false
/execute if entity @e[tag=jog,limit=1] run bossbar set minecraft:jorg visible true