JavaScript — Cache Computation Results in a Local Variable

We’re using a small performance optimization in our code bases: caching computation results in local variables. Saving results in a local variable is borrowed from the memoization technique. Memoizing values improves the performance of function execution by storing the results and reusing them for a function call.

This tutorial shows you how to use local caching of computation results to increase your code’s processing performance.

Node.js Series Overview

  1. String Replace All Appearances
  2. Remove All Whitespace From a String in JavaScript
  3. Generate a Random ID or String in Node.js or JavaScript
  4. Remove Extra Spaces From a String in JavaScript or Node.js
  5. Remove Numbers From a String in JavaScript or Node.js
  6. Get the Part Before a Character in a String in JavaScript or Node.js
  7. Get the Part After a Character in a String in JavaScript or Node.js
  8. How to Check if a Value is a String in JavaScript or Node.js
  9. Check If a String Includes All Strings in JavaScript/Node.js/TypeScript
  10. Check if a Value is a String in JavaScript and Node.js
  11. Limit and Truncate a String to a Given Length in JavaScript and Node.js
  12. Split a String into a List of Characters in JavaScript and Node.js
  13. How to Generage a UUID in Node.js
  14. Reverse a String in JavaScript or Node.js
  15. Split a String into a List of Lines in JavaScript or Node.js
  16. Split a String into a List of Words in JavaScript or Node.js
  17. Detect if a String is in camelCase Format in Javascript or Node.js
  18. Check If a String Is in Lowercase in JavaScript or Node.js
  19. Check If a String is in Uppercase in JavaScript or Node.js
  20. Get the Part After First Occurrence in a String in JavaScript or Node.js
  21. Get the Part Before First Occurrence in a String in JavaScript or Node.js
  22. Get the Part Before Last Occurrence in a String in JavaScript or Node.js
  23. Get the Part After Last Occurrence in a String in JavaScript or Node.js
  24. How to Count Words in a File
  25. How to Shuffle the Characters of a String in JavaScript or Node.js
  26. Append Characters or Words to a String in JavaScript or Node.js
  27. Check if a String is Empty in JavaScript or Node.js
  28. Ensure a String Ends with a Given Character in JavaScript or Node.js
  29. Left-Trim Characters Off a String in JavaScript or Node.js
  30. Right-Trim Characters Off a String in JavaScript or Node.js
  31. Lowercase the First Character of a String in JavaScript or Node.js
  32. Uppercase the First Character of a String in JavaScript or Node.js
  33. Prepend Characters or Words to a String in JavaScript or Node.js
  34. Check if a String is a Number
  35. Convert a String to Buffer
  36. Prevent Line Breaks in String Template Literals
  37. How to Implement a Custom `toString` Method (Coming soon)
  38. What Is `Symbol.toStringTag` and How to Use It (Coming soon)

Use In-Memory Caching for Faster Code Processing

Imagine an Application class that provides details of your project. For example, you’re accessing the application’s name through this Application class. The application name comes from the name property of the package.json file. Here’s the optimization idea: you’re reading and parsing the contents of the package.json file once and keep it memorized in a local property.

Here’s the sample code of the application class that reads and stores the contents of the project’s package.json file:

import Fs from 'node:fs'  
import Path from 'node:path'

export class Application {  
  /**
   * Create a new application instance.
   */
  constructor () {
    this.meta = {
      packageJson: undefined,
    }
  }

  /**
   * Returns the app name.
   */
  name () {
    return this.packageJson().name
  }

  /**
   * Returns the object of the application’s `package.json` file.
   */
  private packageJson () {
    if (this.meta.packageJson != null) {
      return this.meta.packageJson
    }

    const packageJsonPath = Path.resolve(__dirname, 'package.json')

    if (!Fs.existsSync(packageJsonPath)) {
      throw new Error(`Cannot find "package.json" in application base path: "${packageJsonPath}"`)
    }

    this.meta.packageJson = JSON.parse(
      Fs.readFileSync(packageJsonPath).toString()
    )

    return this.meta.packageJson
  }
}

Here’s how you could use the Application class and its memoized values:

const app = new Application()

console.log(app.name())  
// reads the `package.json` file from disk and returns the "name" property from it

console.log(app.name())  
// uses the in-memory `package.json` content and returns the "name" property from it

You can use in-memory caching to store all kinds of computations. Typically, you’re storing resource-intensive results to avoid redundant processing. A good candidate for local caching is the result of reading and parsing a file from local hard disk, because the file may not change until restarting the Node.js process.

That’s it!

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