JSFiddle - React, Tailwind, and code Playground

JavaScript

var measure = [
  {k:"гр",v:1000},
  {k:"кг",v:1},
  {k:"т",v:0.001}
];
var arrMy = [];
for(var i=0;i<measure.length;i++){
arrMy.push(Number(String(measure[i].v).length));
    
}
var res = measure[arrMy.indexOf(Math.min.apply(null, arrMy))];
console.log(res.v+' '+res.k);