Array.filter and Array.map Javascript Polyfills

polyfills.js

// Array.map polyfill
if (Array.prototype.map === undefined) {
  Array.prototype.map = function(fn) {
    var rv = [];
    
    for(var i=0, l=this.length; i<l; i++)
      rv.push(fn(this[i]));

    return rv;
  };
}

// Array.filter polyfill
if (Array.prototype.filter === undefined) {
  Array.prototype.filter = function(fn) {
    var rv = [];
    
    for(var i=0, l=this.length; i<l; i++)
      if (fn(this[i])) rv.push(this[i]);

    return rv;
  };
}

This solution is very risky.
In both polyfills, you are not even doing a sanity check for function supplied as the argument.
And please check the proper signature of filter method.

I agree with @AjayPoshak.

for comparaison here is the map polyfill provided on MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map#Polyfill