webjs ---- 前端下载jpg,pdf之类的

var xhr = new XMLHttpRequest();
        xhr.open('GET', "http://faceunity.com/static/images/index_bc.jpg", true);
        xhr.responseType = "blob";//关键的一步
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4) {
                if (xhr.status == 200) {
                    var blod = this.response;
                    console.log(blod)
                    // var src = URL.createObjectURL(blod);
                    var eleLink = document.createElement("a");
                    eleLink.download = name || new Date().getTime() + ".jpg";
                    eleLink.href = URL.createObjectURL(blod);
                    document.body.appendChild(eleLink);
                    eleLink.click();
                }
            }
        };
        xhr.send();

jquery返回的数据进行了处理，要用原生的