在vue後臺管理系統裡面，有時候會遇到一個圖片上傳的功能，做這個功能的時候的思路是這樣的：
1：首選由前端寫一個圖片上傳的upload標籤，選擇本地的圖片檔案之後
2:呼叫後端給的介面，以二進位制檔案的形式傳給後端伺服器
3:伺服器進行處理，處理完成之後將伺服器的主機名加到圖片名稱的字首上
4:返回一個有伺服器主機+圖片名稱的線上就可以訪問的連結給到前端
5:前端直接將線上連結路徑渲染在介面顯示圖片

在vue-element-admin裡面的具體的實踐

1:在store/modules裡面新建一個api.js
將上傳圖片至伺服器的後端小夥伴給的介面寫在這個js裡面

const baseUrl = 'http://39.xx.xxx.1xx/yyexploreplatform'
const state 
 
= {
  fileUpload: baseUrl + '/upload/file'
}

export default { state }

2：開啟store/getters.js
getters.js

const getters = {
  fileUpload: state => state.api.fileUpload,
}
export default getters

3：新建一個index.vue頁面

開始寫程式碼：

<template>
  <div class="app-container">
        <el-form ref="nextProjectForm" :model="nextProjectForm" label-width="100px">
          <el-form-item label="插入圖片">
            <el-upload
              class
 
="avatar-uploader"
              :action="fileUpload"
              :headers="{ Authorization: token }"
              :show-file-list="false"
              :on-success="handleAvatarSuccess">
         
              <img
                v-if="nextProjectForm.publicWelfareUrl"
                :src
 
="nextProjectForm.publicWelfareUrl"
                class="avatar"/>
              <i v-else class="el-icon-plus avatar-uploader-icon"></i>
            </el-upload>
          </el-form-item>           
        </el-form>
  </div>
</template>
<script>
import { mapGetters } from "vuex";
export default {
  data() {
    return {
      nextProjectForm: {
        publicWelfareUrl: "",
      },
    };
  },
  computed: {
    ...mapGetters(["fileUpload", "token"])
  },
  methods: {
   
    handleAvatarSuccess(response, file, fileList) {
      if (response && response.data && response.data.url) {
        this.$set(this.nextProjectForm, "publicWelfareUrl", response.data.url);
      }
    },
   
  }
};
</script>
<style lang='scss'>
.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-icon {
  font-size: 28px;
  color: #8c939d;
  width: 178px;
  height: 178px;
  line-height: 178px;
  text-align: center;
}
.avatar {
  width: 178px;
  height: 178px;
  display: block;
}
</style>

4:效果如下：

5：有些業務需求是這樣的，給定一個圖片尺寸，比如說最大寬度是500，最大高度是300，如果上傳的圖片尺寸超過這個範圍，在上傳的時候，一個提示，不符合這個尺寸的都無法上傳。
這個時候，就需要進行判斷了

需要在upload裡面新增一個:before-upload方法

然後在 methods裡面寫一下這個方法的實現過程程式碼

 //對圖片大小的限制
    handleImagesUrlBefore:function(file){
                var _this = this;
                return new Promise(function(resolve, reject) {
                    var reader = new FileReader();
                    reader.onload = function(event) {
                        var image = new Image();
                        image.onload = function () {
                            var width = this.width;
                            var height = this.height;
                            if (width>500 ){
                                _this.$alert('圖片寬度尺寸必須在500之內！', '提示', {confirmButtonText: '確定'});
                                reject();
                            }
                            if (height >300) {
                                _this.$alert('圖片高度尺寸必須在300之內！', '提示', {confirmButtonText: '確定'});
                                reject();
                            }
                            resolve();
                        };
                        image.src = event.target.result;
                    }
                    reader.readAsDataURL(file);
                });
            },

完整的參考程式碼：

<template>
  <div class="app-container">
        <el-form ref="nextProjectForm" :model="nextProjectForm" label-width="100px">
          <el-form-item label="插入圖片">
            <el-upload
              class="avatar-uploader"
              :action="fileUpload"
              :before-upload="handleImagesUrlBefore"
              :headers="{ Authorization: token }"
              :show-file-list="false"
              :on-success="handleAvatarSuccess">
         
              <img
                v-if="nextProjectForm.publicWelfareUrl"
                :src="nextProjectForm.publicWelfareUrl"
                class="avatar"/>
              <i v-else class="el-icon-plus avatar-uploader-icon"></i>
            </el-upload>
          </el-form-item>           
        </el-form>
  </div>
</template>
<script>
import { mapGetters } from "vuex";
export default {
  data() {
    return {
      nextProjectForm: {
        publicWelfareUrl: "",
      },
    };
  },
  computed: {
    ...mapGetters(["fileUpload", "token"])
  },
  methods: {
    //對圖片大小的限制
    handleImagesUrlBefore:function(file){
                var _this = this;
                return new Promise(function(resolve, reject) {
                    var reader = new FileReader();
                    reader.onload = function(event) {
                        var image = new Image();
                        image.onload = function () {
                            var width = this.width;
                            var height = this.height;
                            if (width>500 ){
                                _this.$alert('圖片寬度尺寸必須在500之內！', '提示', {confirmButtonText: '確定'});
                                reject();
                            }
                            if (height >300) {
                                _this.$alert('圖片高度尺寸必須在300之內！', '提示', {confirmButtonText: '確定'});
                                reject();
                            }
                            resolve();
                        };
                        image.src = event.target.result;
                    }
                    reader.readAsDataURL(file);
                });
            },

    handleAvatarSuccess(response, file, fileList) {
      if (response && response.data && response.data.url) {
        this.$set(this.nextProjectForm, "publicWelfareUrl", response.data.url);
      }
    },
   
  }
};
</script>
<style lang='scss'>
.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-icon {
  font-size: 28px;
  color: #8c939d;
  width: 178px;
  height: 178px;
  line-height: 178px;
  text-align: center;
}
.avatar {
  width: 178px;
  height: 178px;
  display: block;
}
</style>

如果不符合尺寸的時候，會有一個彈框進行提示

參考資源：