Vue2实时监听表单变化的方法

<template>
<section>
<el-dialog :title="formTitle" :visible.sync="dialogFormVisible" :before-close="cancel">
<el-form :model="form" :rules="rules" ref="form">
</el-form>
<div slot="footer" class="dialog-footer">
<el-button size="medium" type="primary" @click="addSubmit" :loading="addLoading" :disabled="unChange">确 定</el-button>
</div>
</el-dialog>
</section>
</template>

<script>
export default {
props: ["dialogFormVisible","form","formTitle"],
data() {
return {
unChange: true,
preForm: JSON.parse(JSON.stringify(this.form)) //深拷贝对象
};
},
watch: {
form:{
handler:function(nowVal,oldVal){
var $this = this;
for(let i in $this.form){
if(nowVal[i] != $this.preForm[i]) {
$this.unChange = false;
break;
}else {
$this.unChange = true;
}
}
},
deep:true
}
},
methods: {
addSubmit() {
var $this = this;
}
},
mounted() {
var $this = this;
}
};
</script>