2-1 watch

<template>
  <div>
    <input type="text" v-model="word" placeholder="请输入" />
    {{msg}}
  </div>
</template>
<script>
export default {
  name: "Home",
  data() {
    return {
      word: "",
      msg: ""
    };
  },
  watch: {
    word(newVal, oldVal) {
      setTimeout(() => {
        if (newVal.length > 6) {
          return (this.msg = "字符不能大于6位");
        } else if (newVal.length < 3) {
          return (this.msg = "字符不能小于3位");
        }
      }, 1000);
    }
  }
};
</script>

深度监听

watch:{
  arr:{
    handler(newVal){
    },
    deep:true
  }
}