[рони]

xcube,

const datas = [{name : 1, price : 100} , {name : 2, price : 45}, {name : 3, price : 400}],
      datab = [{name : 1, price : 5} , {name : 2, price  : 33}],
      dataz = datab.map((v,i) => {
      const {name} = v , ob = datas.find(({name : k}) => k == name);
      if (ob) v.цена = ob.price;
      return v
      })


console.log(dataz)