项目中此方法用于将网页保存下载为pdf格式，IE不兼容此插件。
解决方法：
Open node_modules/html2canvas/dist/html2canvas.js
Search for if (rule && rule.cssText)
and Change it to if (rule && typeof rule.cssText === 'string')
This fixed the problem for me in IE11
参考：
解决方法：
Open node_modules/html2canvas/dist/html2canvas.js
Search for if (rule && rule.cssText)
and Change it to if (rule && typeof rule.cssText === 'string')
This fixed the problem for me in IE11
参考：
