stratagem/lib/attribute.js

A lightweight node module for simulating turn-based role-playing game battles

import ModifierTypes from './modifier-types.js'

export default class Attribute {
  constructor(base) {
    this.base = base
    this.value = base
    this.modifiers = {}
  }
  setBase(base) {
    this.base = base
    this._calculate()
    return this
  }
  setModifier(id, type, value) {
    this.modifiers[id] = { type, value }
    this._calculate()
    return this
  }
  deleteModifier(id) {
    delete this.modifiers[id]
    this._calculate()
    return this
  }
  getModifier(id) {
    return this.modifiers[id]
  }
  hasModifier(id) {
    return this.modifiers[id] != undefined
  }
  _calculate() {
    let multiplier = 1.0
    let addend = 0
    Object.values(this.modifiers).forEach(({ type, value }) => {
      switch (type) {
        case ModifierTypes.MULTIPLIER:
          multiplier *= value
          break
        case ModifierTypes.ADDEND:
          addend += value
          break
      }
    })
    this.value = (this.base + addend) * multiplier
  }
}