Skills & Passives

Skill bars

Slotted skills matter even though this library computes stats, not damage rotations: the engine uses the active bar to decide conditional effects — skill-line passives (e.g. Destruction Staff passives only apply with a staff skill slotted) and conditional set bonuses.

const stats = calculateBuild({
  character: { /* ... */ },
  skillBars: {
    bar1: [
      { skillId: 28807, morphIndex: 2 }, // Crystal Fragments (second morph)
      { skillId: 24322 },                // Mages' Fury (no morph)
    ],
    bar2: [
      { skillId: 29073, morphIndex: 1 }, // Boundless Storm (first morph)
    ],
  },
  activeWeaponBar: 1, // default — which bar is active
});

Each SkillSlot takes:

Field	Description
skillId	Base (unmorphed) skill ID — the engine's lookup key.
morphSkillId	Optional ability ID of the equipped morph; used to resolve the correct description text.
morphIndex	0 base (default), 1 first morph, 2 second morph.

Up to 6 skills per bar. activeWeaponBar also selects which weapon items (MainHand1/OffHand1 vs MainHand2/OffHand2) count for enchants and set bonuses.

Passives

Passives are unlocked by ability ID. The catalog functions give you the IDs — each passive appears once per rank, so pick the rank you want (usually the last):

import {
  listRacialPassives,      // race passives, e.g. listRacialPassives('High Elf')
  listClassPassives,       // class passives (3 skill lines)
  listPassivesBySkillLine, // any line: 'Heavy Armor', 'Undaunted', 'Destruction Staff', ...
  listAvailableSkillLines, // all valid skill line names
} from 'uesp-eso-build-wrapper';

const passiveIds = [
  ...listRacialPassives('High Elf'),
  ...listClassPassives('Sorcerer'),
  ...listPassivesBySkillLine('Light Armor'),
  ...listPassivesBySkillLine('Undaunted'),
].map((p) => p.abilityId);

const stats = calculateBuild({
  character: { /* ... */ },
  passiveSkills: passiveIds,
});

Each passive's effect is applied by the engine by matching its description text — the same mechanism the UESP editor uses.

Auto racial passives

autoPassives: true mirrors the UESP "Auto Purchase Racial Passives" checkbox: it injects the highest-rank passives for the selected race automatically.

const stats = calculateBuild({
  character: { race: 'High Elf', /* ... */ },
  autoPassives: true,
});

It only covers racial passives — class and skill-line passives must be passed explicitly via passiveSkills.

Inherent passives (armor bonuses/penalties)

The UESP Build Editor loads its own ESO_FREE_PASSIVES baseline by itself — the inherent Light/Medium/Heavy Armor Bonuses and Penalties, racial, craft, and a few free actives. autoInherentPassives: true mirrors that: the engine applies them on top of passiveSkills.

const stats = calculateBuild({
  character: { /* ... */ },
  items: equippedItems,
  autoInherentPassives: true,
});

The armor entries are gated per equipped piece, so with no armor of that weight they contribute nothing. Use listInherentPassives() to enumerate them — for example to mark them as owned in a UI.