js 点击默认另存 ，不是打开 Blob 操作

function savepic(obj) {
    if (memFileObj != undefined) {
        obj = memFileObj;
    }
    else {
        memFileObj = obj;
    }
    if (document.all.a1 == null) {
        objIframe = document.createElement("IFRAME");
        $(objIframe).appendTo("body");
        objIframe.outerHTML = "<iframe name='a1' style='width:0;hieght:0' src='" + $(obj).attr("href") + "'></iframe>";
        re = setTimeout("savepic()", 1);
    }
    else {
        clearTimeout(re);
        pic = window.open($(obj).attr("href"), "a1");
        pic.document.execCommand("SaveAs");
        var _parentElement = $("[name='a1']");
        if (_parentElement) {
            $(_parentElement).remove();
            //_parentElement.removeChild(a1);
        }
    }

其他浏览器，例如Chrome浏览器，可以使用保存blob数据流的办法。

给你两个函数供参考

一个用来保存URL，一个用来保存文本。

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function saveAs(Url,filename){ var blob=new Blob([''], {type:'application/octet-stream'});     var url = webkitURL.createObjectURL(blob);     var a = document.createElementNS(xhtml,'a');     a.href = Url;     a.download = filename;      var e = document.createEvent('MouseEvents');     e.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);     a.dispatchEvent(e);     webkitURL.revokeObjectURL(url); }  function saveText(t,filename){ var mime='text/plain'; saveAs(('data:'+mime+';charset=utf-8;base64,' + Base64.encode(t)),filename) }

function savepic(obj) {
    if (memFileObj != undefined) {
        obj = memFileObj;
    }
    else {
        memFileObj = obj;
    }
    if (document.all.a1 == null) {
        objIframe = document.createElement("IFRAME");
        $(objIframe).appendTo("body");
        objIframe.outerHTML = "<iframe name='a1' style='width:0;hieght:0' src='" + $(obj).attr("href") + "'></iframe>";
        re = setTimeout("savepic()", 1);
    }
    else {
        var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串
        var isOpera = userAgent.indexOf("Opera") > -1;

        clearTimeout(re);
        pic = window.open($(obj).attr("href"), "a1");
        pic.document.execCommand("SaveAs");

        var frameElement = $("[name='a1']");
        if (frameElement) {
            $(frameElement).remove();
        }

//        if (userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1 && !isOpera) { // is ie

//        } else { //not ie

//            saveAs($(obj).attr("href"), $(obj).attr("href").substring($(obj).attr("href").lastIndexOf('/') + 1));
//        }
    }
}

function saveAs(Url, filename) {
    var blob = new Blob([''], { type: 'application/octet-stream' });
    var url = URL.createObjectURL(blob);

    blobSaveAs(blob, filename);
    //    reader.file = file;

    //    reader.onerror = function(e) {
    //        switch (e.target.error.code) {
    //            case e.target.error.NOT_FOUND_ERR:
    //                alert('File Not Found!');
    //                break;
    //            case e.target.error.NOT_READABLE_ERR:
    //                alert('File is not readable');
    //                break;
    //            case e.target.error.ABORT_ERR:
    //                break; // noop
    //            default:
    //                alert('An error occurred reading this file.');
    //        };
    //    };

    //    reader.onabort = function(e) {
    //        alert('File read cancelled');
    //    };
    //    reader.onload = function(e) {
    //        var blob = new Blob(e.target.result, { type: 'application/octet-stream' });
    //        //bb.append(this.result);
    //
    //    }
    //    reader.readAsBinaryString(file);
    //}

}

function blobSaveAs(blob, filename) {
    var type = blob.type;
    var force_saveable_type = 'application/octet-stream';
    if (type && type != force_saveable_type) { // 强制下载，而非在浏览器中打开
        var slice = blob.slice; // || blob.webkitSlice || blob.mozSlice;
        blob = slice.call(blob, 0, blob.size, force_saveable_type);
    }
    var url = URL.createObjectURL(blob);
    var save_link = document.createElementNS('xhtml', 'a');
    save_link.href = url;
    save_link.download = filename;
    var event = document.createEvent('MouseEvents');
    event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
    save_link.dispatchEvent(event);
    URL.revokeObjectURL(url);
}

function readAsBinaryString() {
    var file = document.getElementById("file").files[0];
    var reader = new FileReader();
    //将文件以二进制形式读入页面
    reader.readAsBinaryString(file);
    reader.onload = function(f) {
        var result = document.getElementById("result");
        //显示文件
        result.innerHTML = this.result;
    }
}

<div><input type="file" id="file" />
        <input type="button" value="读取二进制数据" onclick="readAsBinaryString()" />
        <div id="result" name="result"></div></div>