在js中使用两个函数实现一个响应式数据

// createSignal.js
function createSignal(initialValue) {
  let value = initialValue
  const subscribe = new Set()
  const read = () => {
    if (currentListener !== undefined) {
      subscribe.add(currentListener)
    }
    return value
  }
  const write = (newValue) => {
    value = newValue
    subscribe.forEach(fn => fn())
  }
  return [read, write]
}
// createEffect
let currentListener = undefined
function createEffect(callback) {
  currentListener = callback
  callback()
  currentListener = undefined
}

使用示例

const [count, setCount] = createSignal(0)
createEffect(() => {
  console.log(count())
})
createEffect(() => {
  console.log(count(), Date.now())
})
setInterval(() => {
  setCount(count() + 1)
}, 1000)