let x={"1":170,"2":93,"3":-36,"4":0,"5":18,"6":-359,"7":49,"8":105,"9":16,"10":186,"11":48,"12":24,"13":10,"14":111,"15":68,"16":-375,"17":-25,"18":-42,"19":48,"20":64,"21":68,"22":-61,"23":120,"24":81};
console.log(Object.keys(x).length); // количество составляющих
let y=Object.keys(x);
console.log(x[y[y.length-1]]); // последний элемент