Memoization in JS at function level

vishal1025 — Fri, 16 Oct 2020 18:45:24 +0000

I recently encountered an interesting problem wherein you need to achieve a simple memoization at a function level.

Explaining the problem first,

Let's suppose you have been given a function for summation of 2 numbers

add = (a, b) => {
 return a,b
}

You have to write a function let's suppose memoize which receives a function

function memoize(func) {}

Input to the problem

let mem = memoize(add);
console.log(mem(1,2)) => 3
console.log(mem(2,4)) => 6
console.log(mem(1,2)) => 3

So, problem is you need to complete the memoize function to return the output but the catch is if the input params are already being computed then you don't need to compute them again

Solution

So, let's start revising some core concept of JS i.e every function is ultimately an object in JS,🧐🧐

Let's think how we can use this concept in our function memoize

function memoize(func) {

  // Since, we can have a property in objects, right?
  if(!memoize.preInputs) {
    memoize.preInputs = []
  }

return function() {
        for(let i = 0; i < memoize.preInputs.length; i++) {
          if((memoize.preInputs[i]['arg1'] === arguments[0] && 
            memoize.preInputs[i]['arg2'] === arguments[1]) || 
            (memoize.preInputs[i]['arg1'] === arguments[1] && 
            memoize.preInputs[i]['arg2'] === arguments[0])) {
            console.log('precomputed');
            return memoize.preInputs[i]['result'];
          } 
         }
         memoize.preInputs.push({
              arg1: arguments[0],
              arg2: arguments[1],
              result: func(arguments[0], arguments[1])
            });
         console.log('newly calculated');
         return memoize.preInputs[memoize.preInputs.length - 1].result;
        }

Now, let's try using the output,
console.log(mem(1,2))
=> newly calculated
3
console.log(mem(3,4))
=> newly calculated
7
console.log(mem(1,2))
=> precomputed
3

So, that's it this is a one way by which you can achieve this, I am pretty much sure you can have other ways also

Bye!
Happy Coding !!😁😁😁

DEV Community: vishal1025

Memoization in JS at function level