Browser Errors - soares-marcio/js-xlsx GitHub Wiki
SCRIPT5022: DataCloneError
IE10 does not properly support Transferables. Recommendation: do not enable transferable by default for IE. (see https://github.com/SheetJS/js-xlsx/issues/247)
IE: Object doesn't support property or method 'slice'
Be sure to include the shim before loading xlsx.js (see https://github.com/SheetJS/js-xlsx/issues/244)
Gmail API: "TypeError: f.substr is not a function"
Google uses a different base64 encoding. You need to convert it back with a regexp like
XLSX.read(attachment.replace(/_/g, "/").replace(/-/g, "+"), {type:'base64'})
See #625 for a longer discussion.