百度ueditor组件上传图片后如何设置img里的alt属性

function callback(){try{var link, json, loader,body = (iframe.contentDocument || iframe.contentWindow.document).body,result = body.innerText || body.textContent || '';json = (new Function("return " + result))();link = me.options.imageUrlPrefix + json.url;if(json.state == 'SUCCESS' && json.url) {loader = me.document.getElementById(loadingId);loader.setAttribute('src', link);loader.setAttribute('_src', link);loader.setAttribute('title', json.title || '');loader.setAttribute('alt', json.original || '');loader.removeAttribute('id');domUtils.removeClasses(loader, 'loadingclass');} else {showErrorLoader && showErrorLoader(json.state);}}catch(er){showErrorLoader && showErrorLoader(me.getLang('simpleupload.loadError'));}form.reset();domUtils.un(iframe, 'load', callback);}