Memoization is a programming technique that we used to speed up functions and it can be used to do whenever we have an expensive function ( takes a long time to execute). It relies on the idea of cache {}. A cache is just a plain object. It reduces redundant function expression calls.
Let’s understand how to write a simpler code of the Memoization function in JS.
Example 1: In this example, we will see the inefficient way of writing a function that takes more time to compute.
Javascript
const square = (n) => { let result = 0; // Slow function for (let i = 1; i <= n; i++) { for (let j = 1; j <= n; j++) { result += 1; } } return result;}console.log(square(10000006));console.log(square(40));console.log(square(5)); |
Output:
For this reason, to compute operation in less time for large, we use memoization.
There are two ways to do memoization:
- Function memoization
- Cache memoization
Slow function which takes a large time to compute using cache memoization.
Example 2: This example is used to find the Square of number
Javascript
const preValues = []function square(n) { if (preValues[n] != null) { return preValues[n] } let result = 0; for (let i = 1; i <= n; i++) { for (let j = 1; j <= n; j++) { result += 1; } } // Storing precomputing value preValues[n] = result; return result;}console.log(square(50000));console.log(square(5000));console.log(square(500)); |
2500000000 25000000 250000
Uses in Dynamic programming using cache memoization.
Example 3: This example is used to print Fibonacci sequence
Javascript
fib = (n, preValues = []) => { if (preValues[n] != null) return preValues[n]; let result; if (n <= 2) result = 1; else result = fib(n - 1, preValues) + fib(n - 2, preValues); preValues[n] = result; return result;}console.log(fib(100)); |
354224848179262000000
Using memoizer i.e. it takes a function and then it has to return a function.
Example 4: This example shows memoization in Javascript
Javascript
// Memoizerconst memoize = () => { // Create cache for results // Empty objects const results = {}; // Return function which takes // any number of arguments return (...args) => { // Create key for cache const argsKey = JSON.stringify(args); // Only execute func if no cached val // If results object does not have // anything to argsKey position if (!results[argsKey]) { results[argsKey] = func(...args) } return results[argsKey]; };};// Wrapping memoization functionconst multiply = memoize((num1, num2) => { let total = 0; for (let i = 0; i < num1; i++) { for (let j = 0; j < num1; j++) { // Calculating square total += 1 *; } } // Multiplying square with num2 return total * num2;});console.log(multiply(500, 5000)); |
Output:
1250000000
