How to solve in IE11: Object doesn't support property or method 'padStart'

I have code that turns time intervals (sums and averages) into "hh:mm:ss" format just fine everywhere, except in IE 11, where I get this error:

SCRIPT438: Object doesn't support property or method 'padStart'

How can I rewrite this code so it would work?

var times = [3600000, 60000, 1000];

function formatTime(avg) {
    return times.map(function (t) {
        var value = Math.floor(avg / t);
        avg %= t;
        return value;
    }).map(function (v) {
        return v.toString().padStart(2, 0);
    }).join(':');
}

console.log(formatTime(32939000)); // 09:08:59

padStart(2, 0) is called in the last return statement. How can I make it work in IE11?

For your specific case -- where you are dealing with time parts (hours, minutes, seconds), which have either 1 or 2 digits -- you can replace:

return v.toString().padStart(2, 0);

with:

return ("0" + v).slice(-2);

...and why not do that in the first iteration so you can avoid the additional map:

var times = [3600000, 60000, 1000];

function formatTime(avg) {
    return times.map(function (t) {
        var value = Math.floor(avg / t);
        avg %= t;
        return ("0" + value).slice(-2);
    }).join(':');
}

console.log(formatTime(32939000)); // 09:08:59

Another way is to first make the join, and then use \b\d\b as regular expression to spot the single digits and insert the missing zeroes with replace:

.join(':').replace(/\b\d\b/g, "0$&");

var times = [3600000, 60000, 1000];

function formatTime(avg) {
    return times.map(function (t) {
        var value = Math.floor(avg / t);
        avg %= t;
        return value;
    }).join(':').replace(/\b\d\b/g, "0$&");
}

console.log(formatTime(32939000)); // 09:08:59