v-model，主要作用实现了在html标签中与data数据双向绑定，为用户提供了简便快捷的双向绑定使用方式
<body>
<div style="border: 1px solid gray;width: 100px;height: 30px;"></div>
<input type="text" value="">
</body>
<script>
let div = document.querySelector("div")
let ipt = document.querySelector("input")
let data = { val: '' }
ipt.oninput = function (val) {
data.val = ipt.value
}
Object.defineProperty(data, "val", {
get() {
return ipt.value
},
set(value) {
div.innerHTML = ipt.value;
ipt.value = value
}
})
</script>
