In this example, you can format data (rows and cols) became from public Google Sheets API in JSON format.

google-sheets-format-json-data.js

// ----------------------------------------
// IMPORTANT!!!
// ----------------------------------------
// FIRST OF ALL, REMEMBER TO TURN ON PUBLIC READ PERMISSION IN YOUR SPREADSHEET IN GOOGLE.
// ----------------------------------------


// BASE URL TO GET SHEET DATA
sheetsBaseURL = "https://docs.google.com/spreadsheets/d"

// LOAD DATA FROM GOOGLE SHEETS SERVICE
getSheet(id, params='') {
  const xmlHttp = new XMLHttpRequest();
  xmlHttp.open( "GET", `${this.sheetsBaseURL}/${id}/gviz/tq?tqx=out:json${params}`, false ); // false for synchronous request
  xmlHttp.send( null );
  return xmlHttp.responseText;
}

// GET AND FORMAT DATA BY `ROWS`
getByRows(table:any){
  if(table.rows){
    const rows = []
    table.rows.map(r=>{
      if(r.c){
        const cols = [];
        r.c.map((col)=>{
          if(col != null && col.v){
            cols.push(col.v)
          } else {
            cols.push(col)
          }
        })
        rows.push(cols)
      }
    })
    return rows
  }
}

// GET AND FORMAT DATA BY `COLUMNS`
getByCols(table:any){
  if(table.cols){
    const cols = []
    table.cols.map((col,indexCol)=>{
      col.lines = []
      if(table.rows){
        table.rows.map(r=>{
          if(r.c){
            if(r.c[indexCol] != null && r.c[indexCol].v){
              col.lines.push(r.c[indexCol].v)
            } else {
              col.lines.push(r.c[indexCol])
            }
          }
        })
        cols.push(col)
      }
    })
    return cols
  }
}

// GET AND FORMAT DATA BY `MATRIX`
getByMatrix(table:any, keyAsID=true){
  if(table.rows){
    const rows = []
    table.rows.map(r=>{
      if(r.c){
        const cols:any = keyAsID ? {} : []
        r.c.map((colR,indexCol)=>{
          if(colR === null) colR = {}
          colR.id = table.cols[indexCol].id
          colR.label = table.cols[indexCol].label
          colR.value = colR.v ? colR.v : null
          delete colR.v
          if(keyAsID){
            cols[colR.id] = colR
          } else {
            cols.push(colR)
          }
        })
        rows.push(cols)
      }
    })
    return rows
  }
}

// GETTING DATA FROM GOOGLE API...
let sheet:any = this.getSheet('1XRsJinlp_q86el6YTjl_Z7IISIeHdE_m4Gu0hPqiOp-s','&gid=0')

// REMOVING UNECESSARY STRING FROM RESPONSE
sheet = sheet.match(/google\.visualization\.Query\.setResponse\(([\s\S\w]+)\)/);

if (sheet && sheet.length == 2) {
  const obj = JSON.parse(sheet[1]);
  // FORMATING DATA BY MATRIX (using function getByMatrix()
  console.log(this.getByMatrix(obj.table))
}