Compare current row in javascript with previous rows

var cptpac=2;

   // if(dataj[0]['Numero_adhesion'] !==dataj[i]['Numero_adhesion'].length>i)//j{
           dataj[i]['Numero_personne_charge']= cptpac++;                         
  // }

var Numero_adhesion_prec = null;
var cptpac=2;
for(let i=0 ; i< data.length ; i++){ 
  let Numero_adhesion = dataj[i]['Numero_adhesion'];
  if(Numero_adhesion == Numero_adhesion_prec ){
    cptpac++;
  }else{
    cptpac = 2;
  }
  dataj[i]['Numero_personne_charge'] = cptpac;
  Numero_adhesion_prec = var Numero_adhesion;
}