Tutorials

Lodash _.memoize() Function Method

Posted in lodash Tutorial

Updated on Mar 11, 2024

By Mari Selvan

👁️ 38 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the dynamic landscape of JavaScript programming, optimizing function performance is a common goal. Lodash, a feature-rich utility library, provides developers with a multitude of tools, and one such gem is the _.memoize() function method.

This method offers a straightforward way to cache the results of expensive function calls, reducing redundant computations and improving overall efficiency.

🧠 Understanding _.memoize() Method

The _.memoize() function in Lodash enables the caching of function results based on the arguments provided to the function. Subsequent calls with the same arguments retrieve the cached result, bypassing the need for recomputation. This can be particularly beneficial for functions with computationally expensive operations or those frequently called with the same inputs.

💡 Syntax

The syntax for the _.memoize() method is straightforward:

syntax.js

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_.memoize(func, [resolver])

func: The function to memoize.
resolver (Optional): The function to resolve the cache key.

📝 Example

Let's dive into a simple example to illustrate the usage of the _.memoize() method:

example.js

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const _ = require('lodash');

// A function with expensive computation
const expensiveFunction = (x, y) => {
    console.log('Computing...');
    return x + y;
};

// Memoizing the expensive function
const memoizedFunction = _.memoize(expensiveFunction);

// First call triggers computation
console.log(memoizedFunction(3, 4));
// Output: Computing... 7

// Subsequent call uses cached result
console.log(memoizedFunction(3, 4));
// Output: 7 (no additional computation)

In this example, the expensiveFunction is memoized using _.memoize(). The first call triggers the computation, and subsequent calls with the same arguments retrieve the cached result without recomputation.

🏆 Best Practices

When working with the _.memoize() method, consider the following best practices:

Choose Functions Wisely:

Select functions for memoization wisely, focusing on those with expensive computations or functions frequently called with the same inputs.

example.js

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const computePower = (base, exponent) => {
  console.log('Computing...');
  return Math.pow(base, exponent);
};

const memoizedPower = _.memoize(computePower);

console.log(memoizedPower(2, 3)); // Output: Computing... 8
console.log(memoizedPower(2, 3)); // Output: 8 (no additional computation)

Custom Cache Key Resolution:

Use the resolver function to customize how cache keys are resolved, especially when dealing with complex arguments.

example.js

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const complexFunction = ({ x, y }) => {
  console.log('Computing...');
  return x + y;
};

const customResolver = ({ x, y }) => `${x}-${y}`;

const memoizedComplexFunction = _.memoize(complexFunction, customResolver);

console.log(memoizedComplexFunction({ x: 3, y: 4 })); // Output: Computing... 7
console.log(memoizedComplexFunction({ x: 3, y: 4 })); // Output: 7 (no additional computation)

Clearing the Memoization Cache:

If needed, you can clear the memoization cache using the _.memoize.Cache object's clear method.

example.js

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const expensiveOperation = (input) => {
  console.log('Computing...');
  return input * 2;
};

const memoizedOperation = _.memoize(expensiveOperation);

console.log(memoizedOperation(5)); // Output: Computing... 10
console.log(memoizedOperation(5)); // Output: 10 (no additional computation)

// Clearing the memoization cache
memoizedOperation.cache.clear();

console.log(memoizedOperation(5)); // Output: Computing... 10 (computation triggered again)

📚 Use Cases

Recursive Function Optimization:

_.memoize() can be beneficial in optimizing recursive functions by avoiding redundant computations for the same inputs.

example.js

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const fibonacci = _.memoize((n) => {
  console.log('Computing Fibonacci...');
  return n <= 1 ? n : fibonacci(n - 1) + fibonacci(n - 2);
});

console.log(fibonacci(5)); // Output: Computing Fibonacci... (computes and caches results)
console.log(fibonacci(5)); // Output: (retrieves result from cache)

Network Request Memoization:

When making repeated network requests with the same parameters, _.memoize() can cache the results, reducing the number of requests.

example.js

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const fetchUserData = async (userId) => {
  console.log('Fetching user data...');
  // Simulate network request
  return { userId, data: /* ... */ };
};

const memoizedFetchUserData = _.memoize(fetchUserData);

console.log(await memoizedFetchUserData(123)); // Output: Fetching user data...
console.log(await memoizedFetchUserData(123)); // Output: (retrieves result from cache)

Expensive Computations:

Functions involving expensive computations, such as complex mathematical operations, can benefit from _.memoize() to avoid redundant recalculations.

example.js

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const calculateComplexResult = (input) => {
  console.log('Performing complex calculation...');
  // Expensive computation
  return /* ... */;
};
const memoizedComplexCalculation = _.memoize(calculateComplexResult);

console.log(memoizedComplexCalculation(42)); // Output: Performing complex calculation...
console.log(memoizedComplexCalculation(42)); // Output: (retrieves result from cache)

🎉 Conclusion

The _.memoize() function method in Lodash provides a convenient way to optimize function performance by caching results based on function arguments. Whether you're dealing with expensive computations or repetitive function calls, _.memoize() can significantly enhance the efficiency of your JavaScript code.

By adhering to best practices and exploring diverse use cases, you can harness the full potential of the _.memoize() method in your Lodash projects.