function writeActiveRange() {
const ss=SpreadsheetApp.getActive();
const sh=ss.getActiveSheet();
const rg=sh.getActiveRange();
let v=rg.getValues();
console.log(v)
const row=rg.getRow();
const col=rg.getColumn();
v.forEach(function(r,i){r.forEach(function(c,j){v[i][j]=`Row:${row+i},Col:${col+j}`;});});
rg.setValues(v);
}