In JavaScript, it’s commonly used for:
- Recursive functions (like Fibonacci)
- Heavy calculations
- Repeated API/data processing
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The Idea (Simple)
Instead of recalculating:
f(10) → compute again
f(10) → compute again
f(10) → compute again With memoization:
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f(10) → compute once
f(10) → return stored result
f(10) → return stored result Basic Example (Without Memoization)
function fib(n) {
if (n <= 1) return n;
return fib(n - 1) + fib(n - 2);
}This is slow because it recomputes the same values many times.
With Memoization
function memoizedFib() {
const cache = {}; // memory store
return function fib(n) {
if (n in cache) return cache[n]; // return saved result
if (n <= 1) return n;
const result = fib(n - 1) + fib(n - 2);
cache[n] = result; // save result
return result;
};
}
const fib = memoizedFib();
fib(40); // much faster
What’s Happening?
cachestores previous results.- Before computing, the function checks:
- “Have I solved this before?”
- If yes → return it instantly.
- If no → compute and store it.
Generic Memoization Function
function memoize(fn) {
const cache = {};
return function (...args) {
const key = JSON.stringify(args);
if (cache[key]) {
return cache[key];
}
const result = fn(...args);
cache[key] = result;
return result;
};
}Usage:
const slowAdd = (a, b) => a + b;
const fastAdd = memoize(slowAdd);
fastAdd(3, 4); // calculated
fastAdd(3, 4); // from cacheWhy Developers Love Memoization
- Performance boost
- Avoids duplicate work
- Widely used in React (
useMemo,useCallback) - Critical in algorithms & dynamic programming
One-Liner Definition
Memoization is caching function results so the same computation is never done twice.
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