sortByProperty.js

function sortByProperty(property) {
    var sortOrder = 1;
    if(property[0] === "-") {
        sortOrder = -1;
        property = property.substr(1);
    }
    return function (a,b) {
        /* next line works with strings and numbers, 
         * and you may want to customize it to your needs
         */
        var result = (a[property] < b[property]) ? -1 : (a[property] > b[property]) ? 1 : 0;
        return result * sortOrder;
    }
}

const data = {
	AU: [
  	{label: "Sydney", value: 9},
    {label: "Melbourne", value: 9},
    {label: "Brisbane", value: 9}
  ],
  IN: [
    {label: "Punjab", value: 9},
    {label: "Maharashtra", value: 9},
    {label: "Tamil Nadu", value: 9}
  ]
}


const finalOutput = {};
for(var country in data) {
	finalOutput[country] = data[country].sort(sortByProperty("label"))
}

console.log(finalOutput);