How to write a simple code of Memoization function in JavaScript ?

Last Updated : 17 Apr, 2023

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));

Output

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));

Output

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