JSFiddle - React, Tailwind, and code Playground

by radu

JavaScript

var arr1 = [['Albania','1000'],['United Kingdom','1000']],
    arr2 = [['Albania','1000'],['UK','1000']], 
    mergedArray = arr1.concat(arr2),
    sum = {},

    // property is preferred name
    // define aliases in lowercase
    aliases = {
        'uk' : 'United Kingdom'
    };

for (var i = 0, n = mergedArray.length; i !== n; i++) {
    var country = mergedArray[i][0],
        num = parseInt(mergedArray[i][1], 10);

    if (aliases.hasOwnProperty(country.toLowerCase())) {
        country = aliases[country.toLowerCase()];          
    }

    if (sum.hasOwnProperty(country))
        sum[country] += num;        
    else
        sum[country] = num;
}

console.log(sum);