memoization Concept in JavaScript

Memoization is an optimization technique that is used to improve the performance of a function by caching its return values so that it does not need to redo the potentially heavy computations next time it is called.

Note: Not all functions can be memoized; only referential transparent functions

EXAMPLE:.

Generally consider caliculating Fibonacci number.. general javascript code looks as:

function getFibonacci (num) {
  if (num < 2) {
      return num;
  }
  return getFibonacci(num - 1) + getFibonacci(num - 2);
}

alert(getFibonacci(10));     // => 55   (with 177 iterations)

But using Momorizing concept we can achieve it very simpley in less Iterations by declaring a cache array where we can store the already-calculated function values that were returned in previous calls.
Then, instead of invoking the function,we can return these values in subsequent calls to the function..

function getFibonacci (num) {
    var cache = [];
    var fib = function(value) {
        if(value < 2 ) return value;
        if( cache[value] ) return cache[value];
    
        cache[value] = (fib(value -1)) + (fib(value-2));
        return cache[value];
    };

    return fib(num);
}

alert(getFibonacci(10));     // => 55   (with 20 iterations)