Js点击按钮下载文件到本地（兼容多浏览器）

实现点击 用纯 js(非jquery)  下载文件到本地 

自己尝试，加网上找了好久未果，如：

window.open(url)   location.href=url   form表单提交   iframe  体验和浏览器兼容都不完美

还是博客园一兄弟给了方法，非常感谢！

window.downloadFile = function (sUrl) {
    //iOS devices do not support downloading. We have to inform user about this.
    if (/(iP)/g.test(navigator.userAgent)) {
        alert(\'Your device does not support files downloading. Please try again in desktop browser.\');
        return false;
    }

    //If in Chrome or Safari - download via virtual link click
    if (window.downloadFile.isChrome || window.downloadFile.isSafari) {
        //Creating new link node.
        var link = document.createElement(\'a\');
        link.href = sUrl;

        if (link.download !== undefined) {
            //Set HTML5 download attribute. This will prevent file from opening if supported.
            var fileName = sUrl.substring(sUrl.lastIndexOf(\'/\') + 1, sUrl.length);
            link.download = fileName;
        }

        //Dispatching click event.
        if (document.createEvent) {
            var e = document.createEvent(\'MouseEvents\');
            e.initEvent(\'click\', true, true);
            link.dispatchEvent(e);
            return true;
        }
    }

    // Force file download (whether supported by server).
    if (sUrl.indexOf(\'?\') === -1) {
        sUrl += \'?download\';
    }
    window.open(sUrl, \'_self\');
    return true;
}
window.downloadFile.isChrome = navigator.userAgent.toLowerCase().indexOf(\'chrome\') > -1;
window.downloadFile.isSafari = navigator.userAgent.toLowerCase().indexOf(\'safari\') > -1;