perf[UploadExcel]: optimized code (#1552)

Author: PanJiaChen

src/components/UploadExcel/index.vue

@@ -82,8 +82,7 @@ export default {
         const reader = new FileReader()
         reader.onload = e => {
           const data = e.target.result
-          const fixedData = this.fixData(data)
-          const workbook = XLSX.read(btoa(fixedData), { type: 'base64' })
+          const workbook = XLSX.read(data, { type: 'array' })
           const firstSheetName = workbook.SheetNames[0]
           const worksheet = workbook.Sheets[firstSheetName]
           const header = this.getHeaderRow(worksheet)
@@ -95,14 +94,6 @@ export default {
         reader.readAsArrayBuffer(rawFile)
       })
     },
-    fixData(data) {
-      let o = ''
-      let l = 0
-      const w = 10240
-      for (; l < data.byteLength / w; ++l) o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w, l * w + w)))
-      o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w)))
-      return o
-    },
     getHeaderRow(sheet) {
       const headers = []
       const range = XLSX.utils.decode_range(sheet['!ref'])