题解 | #购物面板#

var zjsub = document.querySelector('#zjtaiduola')
var zjadd = document.querySelector('#zjtaishaola')
var klsub = document.querySelector('#kltaiduola')
var kladd = document.querySelector('#kltaishaola')
var zjsl = document.querySelector('#zjsl')
var klsl = document.querySelector('#klsl')
var tota = document.querySelector('#total')

function updateTotal(){
  tota.innerHTML = (zjsl.innerHTML-0) * 28 + (klsl.innerHTML-0) * 5
}

zjsub.onclick = function(){
  if(zjsl.innerHTML>0) zjsl.innerHTML = zjsl.innerHTML - 1
  updateTotal()
}
zjadd.onclick = function(){
  zjsl.innerHTML = zjsl.innerHTML - 0 + 1  //强制将字符转换为数字
  updateTotal()
}
klsub.onclick = function(){
  if(klsl.innerHTML>0) klsl.innerHTML = klsl.innerHTML - 1
  updateTotal()
}
kladd.onclick = function(){
  klsl.innerHTML = klsl.innerHTML - 0 + 1
  updateTotal()
}