polyfills.js

/****************************
What is a Polyfill
How to create a Polyfill
NOT recommended on DOM Objects

Array - justLetter - only keep 
    Strings with a specific letter
    
Date - f$$kinDay - return the day
    of the week with prefix
****************************/
let log = console.log;

if(! Array.prototype.sort){
    log('sort does not exist');
}

if(! Array.prototype.justLetter ){
    //log('justLetter method missing')
    Array.prototype.justLetter = function(letter){
        let arr = this.filter((item)=>{
            if(typeof item != 'string') return false;
            return item.indexOf(letter) > -1;
        });
        return arr;
    }
}
let names = ['abc', 'def', {'a':1}, 'cab', 'dac', 123];
log( names );
log( names.justLetter('d') );

if( ! Date.prototype.f$$kinDay ){
   //log('f$$kinDay method missing')
    Date.prototype.f$$kinDay = function(){
        switch(this.getDay()){
            case 0:
                return 'Today is f$$ckin Sunday';
            case 1:
                return 'Today is f$$ckin Monday';
            case 2:
                return 'Today is f$$ckin Tuesday';
            case 3:
                return 'Today is f$$ckin Wednesday';
            case 4:
                return 'Today is f$$ckin Thursday';
            case 5:
                return 'Today is f$$ckin Friday';
            case 6:
                return 'Today is f$$ckin Saturday';
            
        }
    }
}

log( new Date().f$$kinDay() )