ScriptOJ MVVM（勉强符合题意版本，可以优化地方很多）

mvvm.js

const bindViewToData = (el, data) => {
  Object.keys(data).forEach((k) => {
    let v = data[k]

    Object.defineProperty(data, k, {
      get () {
        return v
      },
      set (nv) {
        v = nv
        applyChanges()
      }
    })
  })
  
  let changes = []
  
  const parse = (el) => {
    Array.from(el.childNodes).forEach((c) => { 
      if(!(c instanceof Text)) parse(c)
      else {
        changes.push(((originExp) => () => {
          insertExpForTextNode(c, originExp)
        })(c.nodeValue))
      }
    })
  }
  
  const insertExpForTextNode = (node, originExp) => {
    const newValue = originExp.replace(/{{[\s\S]+?}}/g, function (exp) {
      exp = exp.replace(/[{}]/g, '')
      return execute(exp)
    })
    if (newValue !== node.nodeValue) node.nodeValue = newValue
  }
  
  const execute = (exp) => {
    return new Function(...Object.keys(data), `return ${exp}`)(...Object.values(data))
  }
  
  const applyChanges = () => {
    setTimeout(() => {
      changes.forEach((f) => f())
    })
  }
  
  parse(el)
  applyChanges()
}