pytha.js

var input = [
  { x: 3, y: 4 },
  { x: 12, y: 5 },
  { x: 8, y: 15 }
];
var result = input.map(function(obj){
   // console.log(Math.sqrt((obj.x*obj.x) + (obj.y*obj.y)));
   return Math.sqrt((obj.x*obj.x) + (obj.y*obj.y));
});

 console.log(result[0] === 5);
 console.log(result[1] === 13);
 console.log(result[2] === 17);