padStart() not working in IE11

Question

I'm using angularjs 1.7.2 and kendo ui scheduler. All routes are working fine in almost all browser except when it comes to padStart() part in IE 11. When padStart code is taken this error shows up

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

let ret = '#' + ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0');

Is there a way we can handle this or an alternative way for implementing padStart

Solution

IE 11 is not supporting this function. Please take a look here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart#Browser_compatibility

What you are looking for are polyfills to fill up missing functions of your browser. The following code also taken from developer.mozilla.org will help you:

// https://github.com/behnammodi/polyfill/blob/master/string.polyfill.js
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
if (!String.prototype.padStart) {
    String.prototype.padStart = function padStart(targetLength,padString) {
        targetLength = targetLength>>0; //truncate if number or convert non-number to 0;
        padString = String((typeof padString !== 'undefined' ? padString : ' '));
        if (this.length > targetLength) {
            return String(this);
        }
        else {
            targetLength = targetLength-this.length;
            if (targetLength > padString.length) {
                padString += padString.repeat(targetLength/padString.length); //append to original to ensure we are longer than needed
            }
            return padString.slice(0,targetLength) + String(this);
        }
    };
}

Edit: As mentioned in the comments, by @Plaute, the function repeat needs also to be polyfilled which can be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat

Or include this snippet:

if (!String.prototype.repeat) {
  String.prototype.repeat = function(count) {
    'use strict';
    if (this == null) {
      throw new TypeError('can\'t convert ' + this + ' to object');
    }
    var str = '' + this;
    count = +count;
    if (count != count) {
      count = 0;
    }
    if (count < 0) {
      throw new RangeError('repeat count must be non-negative');
    }
    if (count == Infinity) {
      throw new RangeError('repeat count must be less than infinity');
    }
    count = Math.floor(count);
    if (str.length == 0 || count == 0) {
      return '';
    }
    // Ensuring count is a 31-bit integer allows us to heavily optimize the
    // main part. But anyway, most current (August 2014) browsers can't handle
    // strings 1 << 28 chars or longer, so:
    if (str.length * count >= 1 << 28) {
      throw new RangeError('repeat count must not overflow maximum string size');
    }
    var maxCount = str.length * count;
    count = Math.floor(Math.log(count) / Math.log(2));
    while (count) {
       str += str;
       count--;
    }
    str += str.substring(0, maxCount - str.length);
    return str;
  }
}

Alternatively, to work around the String.prototype.repeat dependency, use the following line:

padString += Array.apply(null, Array(targetLength)).map(function(){ return padString; }).join("");