input file选择图片回显并压缩体积

html：
<input type="file"  accept="image/*" class="filesBtn" id="addWgBtn" name="outPhotos">

js：
$("#addWgBtn").change(function (e) {
        var files = this.files
        if (files) {
            for (var i = 0; i < files.length; i++) {
                $('.add-wgt').before(
                    '<div class="tr-photo fl" >' +
                    '   <img src="' + URL.createObjectURL(files[i]) + '" alt="">' +
                    '   <span class="btn-del"></span>' +
                    '</div>'
                );
                compressImage(files[i], file => {//压缩
                  console.log(file) //压缩后的图片
                }, "");
            }
        }
        $("#addWgBtn").val("")
    })

    // 压缩图片压缩图片压缩图片压缩图片压缩图片压缩图片压缩图片压缩图片
    compressImage = (file, success, error) => {
        // 图片小于1M不压缩
        if (file.size < Math.pow(1024, 2)) {
            return success(file);
        }

        const name = file.name; //文件名
        const reader = new FileReader();
        reader.readAsDataURL(file);
        reader.onload = e => {
            const src = e.target.result;

            const img = new Image();
            img.src = src;
            img.onload = e => {
                const w = img.width;
                const h = img.height;
                const quality = 0.2; // 默认图片质量为0.92
                // 生成canvas
                const canvas = document.createElement('canvas');
                const ctx = canvas.getContext('2d');
                // 创建属性节点
                const anw = document.createAttribute("width");
                anw.nodeValue = w;
                const anh = document.createAttribute("height");
                anh.nodeValue = h;
                canvas.setAttributeNode(anw);
                canvas.setAttributeNode(anh);

                // 铺底色 PNG转JPEG时透明区域会变黑色
                ctx.fillStyle = "#fff";
                ctx.fillRect(0, 0, w, h);

                ctx.drawImage(img, 0, 0, w, h);
                // quality值越小，所绘制出的图像越模糊
                const base64 = canvas.toDataURL('image/jpeg', quality); // 图片格式jpeg或webp可以选0-1质量区间

                // 返回base64转blob的值
                // console.log(`原图${(src.length / 1024).toFixed(2)}kb`, `新图${(base64.length / 1024).toFixed(2)}kb`);
                // 去掉url的头，并转换为byte
                const bytes = window.atob(base64.split(',')[1]);
                // 处理异常,将ascii码小于0的转换为大于0
                const ab = new ArrayBuffer(bytes.length);
                const ia = new Uint8Array(ab);
                for (let i = 0; i < bytes.length; i++) {
                    ia[i] = bytes.charCodeAt(i);
                }
                file = new Blob([ab], {
                    type: 'image/jpeg'
                });
                file.name = name;

                success(file);
            }
            img.onerror = e => {
                error(e);
            }
        }
        reader.onerror = e => {
            error(e);
        }
    }