Property or method “btn“ is not defined on the instance but referenced during render. 报错原因及解决措施_button is not defined

 [Vue warn]: Property or method "btn" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property.

报错原因：属性或方法“btn”未在实例上定义，但在渲染过程中被引用。通过初始化该属性，确保该属性在数据选项中或对于基于类的组件是被动的。一般出现这种情况通常是方法未在methods中定义，或者定义了但是拼写错误，检查拼写。

<template>
  <footer class="footer" v-if="flag">
    <ul class="filters">
      <li>
        <a
          :class="{ selected: isSel == 'all' }"
          href="javascript:;"
          @click="btn('all')"
          >全部</a
        >
      </li>
      <li>
        <a
          :class="{ selected: isSel == 'no' }"
          href="javascript:;"
          @click="btn('no')"
          >未完成</a
        >
      </li>
      <li>
        <a
          :class="{ selected: isSel == 'yes' }"
          href="javascript:;"
          @click="btn('yes')"
          >已完成</a
        >
      </li>
    </ul>
  </footer>
</template>

<script>
export default {
  props: ["flag", "list"],
  data() {
    return {
      isSel: "all",
    };
  },
  methods: {
    bth(num) {
      this.isSel = num;
      console.log(num);
    },
  },
};
</script>

 解决方式：找了半天错误，发现我把btn这个函数写成了bth！

救命！家人们！太粗心了！这个错误总结下！下次不能再犯了！！！！