code: function parseCellStyle(xf, numFmts) {
    const style = {}
    if (xf.hasAttribute('numFmtId')) {
      const numberFormatId = xf.getAttribute('numFmtId')
      if (numFmts[numberFormatId]) {
        style.numberFormat = numFmts[numberFormatId]
      } else {
        style.numberFormat = { id: numberFormatId }
      }
    }
    return style
  }
docs: http://www.datypic.com/sc/ooxml/e-ssml_xf-2.html