wft-utils/just-play/mini-vue/lib/reactive_v2.js

The commonly used tool functions in daily development

class Dep {
  constructor() {
    this.subscribers = new Set()
  }

  depend () {
    if (activeEffect) {
      this.subscribers.add(activeEffect)
    }
  }

  notify () {
    this.subscribers.forEach(effect => {
      effect()
    })
  }
}

let activeEffect = null
function watchEffect (effect) {
  activeEffect = effect
  effect()
  activeEffect = null
}

const targetMap = new WeakMap()
function getDep (target, key) {
  let depsMap = targetMap.get(target)
  if (!depsMap) {
    depsMap = new Map()
    targetMap.set(target, depsMap)
  }
  let dep = depsMap.get(key)
  if (!dep) {
    dep = new Dep()
    depsMap.set(key, dep)
  }
  return dep
}

function reactive (raw) {
  Object.keys(raw).forEach(key => {
    const dep = getDep(raw, key)
    let value = raw[key]
    Object.defineProperty(raw, key, {
      get () {
        dep.depend()
        return value
      },
      set (newValue) {
        if (newValue !== value) {
          value = newValue
          dep.notify()
        }
      }
    })
  })
  return raw
}