JS Master Class - Homework #2

// Part 1.
// Implement a function prototype extension that caches function results for
// the same input arguments of a function with one parameter.

Function.prototype.cached = function() {
  var cache = {},
      func = this;

  return function( arg ) {
    return cache[ arg ] = arg in cache ? cache[ arg ] : func(arg);
  };

};


// Part 2.
// Use this new function to refactor the code example.

function isPrime( num ) { 
  // everything but 1 can be prime
  var prime = num != 1;
  for ( var i = 2; i < num; i++ ) { 
    if ( num % i == 0 ) { 
      prime = false; 
      break; 
    }
  }
  console.log('prime it');
  return prime;
}
var cachedIsPrime = isPrime.cached();
cachedIsPrime(11);
cachedIsPrime(11);


var cachedSin = function( num ) {
  console.log('sine it');
  return Math.sin(num);
}.cached();

cachedSin(1);
cachedSin(1);