iview upload 上传图片前使用Promise判断高宽

因项目需要,上传图片前要验证图片的高宽,看了一下官方文档,before-upload可以返回false或者Promise,就通过promise实现了这个功能.
(ps:里面有用到vuex保存上传七牛的设置,可以根据自己的需要增删)

下面上代码:

• test.vue html

<Upload ref="detailUpload" :show-upload-list="false" :before-upload="detailBeforeUpload" :on-success="detailSuccess" :format="['jpg','jpeg','png']" :max-size="4096" :accept="'image/*'" :on-format-error="handleFormatError" :on-exceeded-size="handleMaxSize" :action="$store.state.qnSetting.upurl ?$store.state.qnSetting.upurl:  'http://upload-z2.qiniup.com'" :data="{token:$store.state.qnSetting.token}">
      <div class="detail-camera-content">
           <Icon type="camera" size="50"></Icon>
     </div>
</Upload>

• test.vue js

//return  promise
detailBeforeUpload(file) {
   return this.checkImageWH(file, 706, 397);
}

//checkImageWH  返回一个promise  检测通过返回resolve  失败返回reject组织图片上传
        checkImageWH(file, width, height) {
            let self = this;
            return new Promise(function (resolve, reject) {
                let filereader = new FileReader();
                filereader.onload = e => {
                    let src = e.target.result;
                    const image = new Image();
                    image.onload = function () {
                        if (width && this.width != width) {
                            self.$Notice.error({
                                title: '请上传宽为' + width + "的图片",
                            });
                            reject();
                        } else if (height && this.height != height) {
                            self.$Notice.error({
                                title: '请上传高为' + height + "的图片",
                            });
                            reject();
                        } else {
                            resolve();
                        }
                    };
                    image.onerror = reject;
                    image.src = src;
                };
                filereader.readAsDataURL(file);
            });
        }