JavaScript Masters Class - Exercise 7

gistfile1.js

function convertToArray(iterable) {
	return Array.prototype.slice.call(iterable);
}

Function.prototype.cached = function() {
	var __method = this;

  // This is to ensure there is only one argument, otherwise just return the results of the calling method.
  if (__method.length != 1)
  {
    console.log("Cannot cache this method (" + __method.name + ") because there is not exactly one argument");
    return function() {
      return __method.apply(this, convertToArray(arguments)); 
    }
  }

	__method.cache = {};
  
  return function() {
    var argToProcess = arguments[0];
		
		if (__method.cache[argToProcess] != null)
		{
			console.log("Cache hit argument: " + argToProcess);
			return __method.cache[argToProcess];
		}
		
		console.log("Cache miss argument: " + argToProcess);
		__method.cache[argToProcess] = __method.apply(this, [argToProcess])
		return __method.cache[argToProcess];
	}
}

var sin = Math.sin.cached();

var runTests = function() {
  console.log(sin(1)); // Output - Cache miss argument: 1
  console.log(sin(2)); // Output - Cache miss argument: 2
  console.log(sin(1)); // Output - Cache hit argument: 1
  console.log(sin(2)); // Output - Cache hit argument: 2
}

runTests();

// This will print - 
var unCachableMethod = function unCachableFunc(a, b) {
  console.log("This is a: " + a);
  console.log("This is b: " + b);
}.cached(); // Output - Cannot cache this method (unCachableFunc) because there is not exactly one argument

unCachableMethod("paramA", "paramB");
// Output -
// This is a: paramA
// This is b: paramB