Efficient Code Practices: Optimize JavaScript Functions

21.5 Best Practices for Efficient Code

In the world of programming, writing efficient code is crucial. Efficient code not only runs faster but also consumes fewer resources, making your applications more responsive and scalable. In this section, we’ll explore best practices for writing efficient JavaScript code, focusing on functions and scope. We’ll cover minimizing redundant calculations, leveraging built-in functions, lazy evaluation, and writing clean, readable code that doesn’t compromise performance.

Minimize Redundant Calculations

One of the simplest yet most effective ways to optimize your code is to minimize redundant calculations. This means avoiding repeated computations that can be calculated once and reused.

Example: Inefficient vs. Optimized Code

Consider the following example where we calculate the square of a number multiple times:

// Inefficient code
function calculateArea(radius) {
  return Math.PI * radius * radius;
}

function calculateCircumference(radius) {
  return 2 * Math.PI * radius;
}

function printCircleProperties(radius) {
  console.log('Area:', calculateArea(radius));
  console.log('Circumference:', calculateCircumference(radius));
  console.log('Diameter:', 2 * radius);
}

printCircleProperties(5);

In the above code, Math.PI is accessed multiple times. Although this is a trivial example, in more complex calculations, such redundancy can lead to performance issues.

Let’s optimize it:

// Optimized code
function printCircleProperties(radius) {
  const pi = Math.PI;
  const area = pi * radius * radius;
  const circumference = 2 * pi * radius;
  const diameter = 2 * radius;

  console.log('Area:', area);
  console.log('Circumference:', circumference);
  console.log('Diameter:', diameter);
}

printCircleProperties(5);

By storing Math.PI in a variable, we reduce the number of times it is accessed, making the code slightly more efficient.

Use Built-in Functions

JavaScript engines are optimized to execute built-in functions efficiently. Whenever possible, use these functions instead of writing custom implementations.

Example: Using Built-in Functions

Let’s say we need to find the maximum number in an array. Instead of writing our own function, we can use the built-in Math.max function combined with the spread operator:

// Custom implementation
function findMax(arr) {
  let max = arr[0];
  for (let i = 1; i < arr.length; i++) {
    if (arr[i] > max) {
      max = arr[i];
    }
  }
  return max;
}

console.log(findMax([5, 3, 9, 1])); // Output: 9

// Using built-in function
const numbers = [5, 3, 9, 1];
const maxNumber = Math.max(...numbers);
console.log(maxNumber); // Output: 9

The built-in function is not only more concise but also potentially faster due to engine optimizations.

Lazy Evaluation and Short-Circuiting

Lazy evaluation is a strategy where expressions are not evaluated until their values are needed. In JavaScript, this concept is often used with logical operators for short-circuiting.

Example: Short-Circuiting

Logical operators like && and || can be used to short-circuit expressions, which can prevent unnecessary calculations.

// Short-circuiting example
function getUserName(user) {
  return user && user.name || 'Guest';
}

const user1 = { name: 'Alice' };
const user2 = null;

console.log(getUserName(user1)); // Output: Alice
console.log(getUserName(user2)); // Output: Guest

In the example above, user && user.name will only evaluate user.name if user is truthy, preventing potential errors and unnecessary evaluations.

Write Clean and Readable Code

Efficiency is not just about speed; it’s also about maintainability. Clean, readable code is easier to understand and optimize.

Example: Clean Code

Consider the following function:

// Less readable code
function calc(a, b, c) {
  return a * b + c;
}

// More readable code
function calculateTotalPrice(price, quantity, tax) {
  return price * quantity + tax;
}

The second example uses descriptive variable names, making the code easier to understand and maintain.

Try It Yourself

Experiment with the following code by modifying it to see how changes affect performance and readability:

function calculateDiscountedPrice(price, discount) {
  const discountAmount = price * (discount / 100);
  return price - discountAmount;
}

console.log(calculateDiscountedPrice(100, 10)); // Output: 90

Try changing the discount calculation to use a different formula or add additional parameters to see how it impacts the function’s efficiency and readability.

Visualizing Code Efficiency

To better understand how efficient code works, let’s visualize the process of optimizing a function using a flowchart.

    flowchart TD
	  A[Start] --> B[Identify Redundant Calculations]
	  B --> C[Use Built-in Functions]
	  C --> D[Apply Lazy Evaluation]
	  D --> E[Write Clean Code]
	  E --> F[End]

This flowchart represents a simple process for optimizing code: start by identifying redundant calculations, use built-in functions, apply lazy evaluation, and write clean code.

References and Further Reading

• MDN Web Docs: JavaScript Performance
• W3Schools: JavaScript Optimization

Knowledge Check

• What is lazy evaluation, and how can it improve performance?
• How can using built-in functions enhance code efficiency?
• Why is it important to write clean and readable code?

Practice Problems

1. Refactor a function that calculates the sum of an array to use a built-in function.
2. Identify and eliminate redundant calculations in a given piece of code.
3. Use short-circuiting to simplify a function that checks multiple conditions.

Embrace the Journey

Remember, this is just the beginning. As you progress, you’ll build more complex and interactive web pages. Keep experimenting, stay curious, and enjoy the journey!

Quiz Time!