how to combine object of array in javascript code example

Example 1: javascript combine objects

const obj1 = {'a': 1, 'b': 2};
const obj2 = {'c': 3};
const obj3 = {'d': 4};

const objCombined = {...obj1, ...obj2, ...obj3};

Example 2: js combine 2 array to object key value

var columns = ["Date", "Number", "Size", "Location", "Age"];
var rows = ["2001", "5", "Big", "Sydney", "25"];
var result =  rows.reduce(function(result, field, index) {
  result[columns[index]] = field;
  return result;
}, {})

console.log(result);