Convert time From milliseconds to minutes in javascript

timeCalculation.js

function timeCalc(millis) {
    var minutes = Math.floor(millis / 60000)
    var seconds = parseInt(((millis % 60000) / 1000).toFixed(0))
    return minutes + ':' + (seconds < 10 ? '0' : '') + seconds
}


let start = new Date().getTime()

/** operation .... */

let end = new Date().getTime();

console.log(
    'Execution time: ',
    timeCalc(new Date(end - start))
)