Error: Expecting a function in instanceof check, but got undefined

[jojohappy]

运行 font-spider 时报错

Error: Expecting a function in instanceof check, but got undefined
    at /Users/works/font_spider/node_modules/font-spider/src/spider/index.js:277:36
    at cssRuleListFor (/Users/works/font_spider/node_modules/font-spider/src/spider/index.js:348:21)
    at FontSpider.eachCssRuleList (/Users/works/font_spider/node_modules/font-spider/src/spider/index.js:330:13)
    at FontSpider.getWebFonts (/Users/works/font_spider/node_modules/font-spider/src/spider/index.js:276:14)
    at FontSpider.parse (/Users/works/font_spider/node_modules/font-spider/src/spider/index.js:44:29)
    at new FontSpider (/Users/works/font_spider/node_modules/font-spider/src/spider/index.js:27:17)
    at /Users/works/font_spider/node_modules/font-spider/src/spider/index.js:403:20
    at process._tickCallback (node.js:369:9)

无论是全局安装，还是当前目录安装都会有这个错误，经过 DEBUG 后发现，window.CSSFontFaceRule is undefined, 在去掉 if 判断后正常

//if (cssRule instanceof CSSFontFaceRule) {
    var webFont = WebFont.parse(cssRule);
    if (webFont) {
        webFonts.push(webFont);
    }
//}

环境信息如下：

• macOS 10.12.2
• Nodejs 4.4.5
• Npm 3.10.9
• font-spider 1.3.3

└─┬ font-spider@1.3.3
  ├─┬ browser-x@0.0.1-beta6
  │ ├── css-mediaquery@0.1.2
  │ ├── cssom@0.3.2
  │ ├── cssstyle@0.2.37
  │ ├── nwmatcher@1.3.9
  │ ├── parse5@2.2.3
  │ ├── specificity@0.1.6
  │ └─┬ verror@1.9.0
  │   ├── assert-plus@1.0.0
  │   ├── core-util-is@1.0.2
  │   └── extsprintf@1.3.0

[imfenghuang]

@aui

1.3.4

这个报这个错误
Error: Expecting a function in instanceof check, but got undefined

删除上述if可以使用