js代码不按顺序执行以及解决方法

1、不按顺序执行的代码（主要是initCourseForm的方法）

<template>
  <div class="app-container">
    <el-steps :active="1" finish-status="success">
      <el-step title="填写课程基本信息"></el-step>
      <el-step title="创建课程大纲"></el-step>
      <el-step title="提交审核"></el-step>
    </el-steps>

    <el-form label-width="120px">
      <el-form-item label="课程标题">
        <el-input v-model="courseInfo.title" placeholder="示例:Java基础课,从0入门,学完可掌握基础知识"></el-input>
      </el-form-item>
      <!--所属分类-->

      <el-form-item label="课程类别">
        <el-select v-model="courseInfo.subjectParentId" placeholder="一级分类" @change="getTwoSubjectList">
          <el-option v-for="info in oneSubjectTitle" :key="info.id" :label="info.title" :value="info.id">
          </el-option>
        </el-select>
        <el-select v-model="courseInfo.subjectId" placeholder="二级分类">
          <el-option v-for="info in twoSubjectTitle" :key="info.id" :label="info.title" :value="info.id">
          </el-option>
        </el-select>
      </el-form-item>


      <!--课程讲师ID-->
      <el-form-item label="课程讲师">
        <el-select v-model="courseInfo.teacherId">
          <el-option v-for="teacher in teacherList" :key="teacher.id" :label="teacher.name" :value="teacher.id">
          </el-option>
        </el-select>
      </el-form-item>

      <el-form-item label="总课时">
        <el-input-number :min="0" v-model="courseInfo.lessonNum" controls-position="right" />
      </el-form-item>
      <!--课程简介-->
      <el-form-item label="课程简介">
        <tinymce :height="300" v-model="courseInfo.description"></tinymce>
      </el-form-item>
      <!--课程封面图片路径ID-->
      <el-form-item label="讲师头像">
        <el-upload :action="BASE_API + '/admin/oss/file/upload'" :show-file-list="false" :on-success="handleSuccess"
          :on-error="handleError" :before-upload="beforeUpload" class="avatar-uploader">
          <img :src="courseInfo.cover">

        </el-upload>
      </el-form-item>

      <el-form-item label="课程价格">
        <el-input-number :min="0" v-model="courseInfo.price" controls-position="right"
          placeholder="课程销售价格，设置为0则可免费观看" />
      </el-form-item>

      <el-form-item>
        <el-button style="margin-top: 12px" type="primary" :disabled="saveBtnDisabled" @click="saveOrUpdate">保存并下一步
        </el-button>
      </el-form-item>
    </el-form>
  </div>
</template>

<script>
import courseApi from "@/api/course";
import teacherApi from "@/api/teacher";
import subjectApi from "@/api/subject";
import Tinymce from "@/components/Tinymce";
const defaultForm = {
  title: '',
  SubjectId: '',//课程专业ID 
  teacherId: '',//课程讲师ID
  description: '',//课程简介
  lessonNum: '',//总课时
  cover: '/static/img/default.jpg',//课程封面图片路径
  price: '',//"课程销售价格，设置为0则可免费观看
}
export default {
  components: { Tinymce },
  data() {
    return {
      courseInfo: defaultForm,
      saveBtnDisabled: false,
      BASE_API: process.env.BASE_API,
      teacherList: [],//所有讲师,
      oneSubjectTitle: [],//一级分类
      twoSubjectTitle: [],//二级分类
    };
  },
  created() {
    this.init()
  },
  watch: {
    $$route(to, from) {
      this.init()
    }
  },
  methods: {
    init() {

      //获取讲师列表
      this.initListTeachers()

      // //获取一级分类
      // this.initSubjectTreeList()

      if (this.$route.params && this.$route.params.id) {
        this.initCourseForm(this.$route.params.id)
      } else {
        //获取所有分类
        this.initSubjectTreeList()
        this.courseInfo = { ...defaultForm }
      }
    },
    //取得课程基本信息和课程简介
    initCourseForm(id) {
      debugger
      courseApi.getCourseForm(id).then(res => {
        if (res.code === 20000 && res.data.data) {
          this.courseInfo = res.data.data
          let value = this.courseInfo.subjectParentId
          //获取一级分类
          this.initSubjectTreeList()
          let tempOneSbujectList = this.oneSubjectTitle.filter(item => item.id === value && item.id);
          this.twoSubjectTitle = tempOneSbujectList[0].childList

          if (!this.twoSubjectTitle.includes(this.courseInfo.subjectId) && this.courseInfo.subjectId) {
            this.courseInfo.subjectId = ''
          }

        }
      }) 
    },
    handleSuccess(res) {
      if (res.success) {
        this.$message.success(res.message);
        this.courseInfo.cover = res.data.url;
        this.$forceUpdate();
      } else {
        this.$message.error(res.message);
      }
    },
    handleError(res) {
      this.$message.error(res.message);
    },
    beforeUpload(file) {
      let isJpg = file.type === "image/jpeg";
      if (!isJpg) {
        this.$message.error("上传头像图片只能是JPG格式！");
        return false;
      }
      let isLt2M = file.size / 1024 / 1024 < 2;
      if (!isLt2M) {
        this.$message.error("上传头像图片不能超过2MB！");
        return false;
      }
      return true;
    },
    //点击一级分类，显示二级分类
    getTwoSubjectList(value) {

      //选中一级分类，在改变一级分类，二级分类显示的数据没有清空的问题
      // this.courseInfo.subjectId = ''   

      let tempOneSbujectList = this.oneSubjectTitle.filter(item => item.id === value && item.id);
      this.twoSubjectTitle = tempOneSbujectList[0].childList

      if (!this.twoSubjectTitle.includes(this.courseInfo.subjectId) && this.courseInfo.subjectId) {
        this.courseInfo.subjectId = ''
      }

    },
    //获取所有讲师
    initListTeachers() {
      teacherApi.listAllTeachers().then(res => {

        if (res.code === 20000 && res.data.list) {
          this.teacherList = res.data.list
        }
      })
    },
    //获取所有分类
    initSubjectTreeList() {
      debugger
      subjectApi.treeList().then(res => {
        if (res.code === 20000 && res.data.treeList) {
          this.oneSubjectTitle = res.data.treeList
        }

      })
    },

    saveOrUpdate() {
      this.saveBtnDisabled = true
      if (this.courseInfo.id) {
        this.updateCourseInfo()
      } else {
        this.saveCourseInfo()
      }
    },
    saveCourseInfo() {
      courseApi.saveCourseInfo(this.courseInfo).then(res => {
        this.$message({
          type: "info",
          message: "保存成功",
        });
        this.$router.push({ path: '/course/editChapter/1' })
      })
    },
    updateCourseInfo() {
      this.$router.push({ path: '/course/editChapter/1' })
    }
  },
};
</script>

<style scoped>
.avatar-uploader .el-upload {
  border: 1px dashed #d9d9d9;
  border-radius: 6px;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}

.avatar-uploader .el-upload:hover {
  border-color: #409EFF;
}

.avatar-uploader .avatar-uploader-icon {
  font-size: 28px;
  color: #8c939d;
  width: 640px;
  height: 357px;
  line-height: 178px;
  text-align: center;
}

.avatar-uploader img {
  width: 640x;
  height: 357px;
  display: block;
}
</style>

 

2、修改方案（两种一种是promise另一种是注释部分this.initSubjectTreeList()方法不这么写，直接写完整的方法调用）

//取得课程基本信息和课程简介
    initCourseForm(id) {
      new Promise((resolve, reject) => {
        courseApi.getCourseForm(id).then(res => {
          if (res.code === 20000 && res.data.data) {
            //基本信息和课程简介回显
            this.courseInfo = res.data.data
          }
          resolve(res.data.data)
        })
      }).then(res => {
        let value = this.courseInfo.subjectParentId
        //一级二级分类回显
        subjectApi.treeList().then(res => {
          if (res.code === 20000 && res.data.treeList) {
            this.oneSubjectTitle = res.data.treeList
            let tempOneSbujectList = this.oneSubjectTitle.filter(item => item.id === value && item.id);
            this.twoSubjectTitle = tempOneSbujectList[0].childList

          }

        })
      })

      // courseApi.getCourseForm(id).then(res => {
      //   if (res.code === 20000 && res.data.data) {
      //     //基本信息和课程简介回显
      //     this.courseInfo = res.data.data
      //     let value = this.courseInfo.subjectParentId
      //     //一级二级分类回显
      //     subjectApi.treeList().then(res => {
      //       if (res.code === 20000 && res.data.treeList) {
      //         this.oneSubjectTitle = res.data.treeList
      //         let tempOneSbujectList = this.oneSubjectTitle.filter(item => item.id === value && item.id);
      //         this.twoSubjectTitle = tempOneSbujectList[0].childList

      //       }

      //     })


      //   }
      // })

    },