Vue2 侦听器 watch【初识】

<div id="app">
<input type="text" v-model="msg">
</div>
<script>
let vm = new Vue({
el: '#app',
data: {
msg: 'Hello'
},
watch: {
msg: function(){
console.log(this.msg)
}
}
})
</script>

<div id="app">
用户名: <input type="text" name="name" v-model.lazy="username">
<span :style="msgStyle">{{ msg }}</span>
<br>
密码: <input type="password" name="pass">
</div>
<script>
let vm = new Vue({
el: '#app',
data: {
msg: '',
username: '',
msgStyle: ''
},
watch: {
username: function(){
// 发送ajax请求 验证用户名
if (this.username == 'liang') {
this.msg = '该用户名已存在'
this.msgStyle = {
color: 'red',
fontWeight: 'bold'
}
} else {
this.msg = '用户名可以注册'
this.msgStyle = {
color: 'green',
fontWeight: 'bold',
}
}
}
}
})
</script>