JS原生操作DOM（更新中）
// 添加查看原图按钮
let grands = document.getElementsByClassName("item-detail");
for(let i=0; i<grands.length; i++){
let oImgs = grands[i].getElementsByTagName("img");
for(let j=0; j<oImgs.length; j++){
let oDiv = document.createElement("div");
let oBtn = document.createElement("input");
oBtn.setAttribute('data-src', oImgs[j].src);
oBtn.setAttribute('type','button');
oBtn.setAttribute('class', 'seeBigPic');
oBtn.setAttribute('value', '查看原图');
// 通过img宽度设置按钮left
oBtn.setAttribute('style', 'left:' + (oImgs[j].width/2 - 39) + 'px');
var p = oImgs[j].parentNode;
p.insertBefore(oDiv, oImgs[j]);
oDiv.appendChild(oImgs[j]);
oDiv.appendChild(oBtn);
oDiv.setAttribute('style', 'position: relative');
}
}