What are the best practices to be followed while using JavaScript?

In this tutorial, we will learn the best practices to follow while using JavaScript.

JavaScript is used in almost every website to make it more user interactive. Throughout the years, ECMAScript has released different versions of JavaScript. Each version has enhanced functionalities and new features, so it is important to know the best practices to follow while using JavaScript.

The following are the best practices to be followed while using JavaScript −

Meaningful Variable and Function Name

The variables’ and functions’ names should be meaningful to their uses. In JavaScript, we use the variable to store some data, and the function is used to execute a set of tasks repetitively. Most beginners use variable names like ‘x’, ‘abc’, ‘a1’ etc.; by reading the variable name, we can’t understand what the variable is storing. It is also hard for another person to understand your code. Similarly, if you store the user’s age in a variable named ‘age’ instead of ‘a’, it will be easy to understand the code. So always use meaningful names for your variables and functions.

// Bad variable name
let a = 20
let x1 = 'Tutorialspoint'

// Good variable name
let age = 20
let name = 'Tutorialspoint'

Use Comments

Comments are the lines of code that did not execute by the compiler; it is used to describe the code or the functionality of a set of code. Comments are useful if multiple people collaborate on a project and for your future reference. Always use the comments whenever needed, and don’t write unnecessary comments on each line of your code. In JavaScript, we use ‘//’ to write a comment.

// It is the comment

Use Local Variables Instead of Global

In JavaScript, accessing the local variables is faster than the global variables, so it is recommended to use them as much as possible. The time it takes to access a variable decrease if all variables are specified in the local scope. Additionally, local variables are destroyed after the completion of a function call, whereas global variables retain their value in memory, potentially resulting in memory problems. Use ‘let’ and ‘const’ to declare local variables instead of using ‘var’ to declare global variables

// Don't use global variables
var language = 'JavaScript'

// Use local variables
const name = 'Tutorialspoint'
let age = 18

Use ‘===’ In The Comparison Instead of ‘==’

In JavaScript, the ‘==’ operator checks whether the values are the same or not, wear as the ‘===’ operator matches the values as well as the types of the values. So, the ‘==’ operator will return true for the comparison between 1 and ‘1’, where both are different types of values. But, in this case, the ‘===’ operator will return false because it also checks the types of the variable.

// Don't use '==' operator
if(value1 == value2){ ... }

// Use '===' operator
if(value1 === value2){ ... }

End Switch with Default Statement

In JavaScript, the switch statement checks multiple conditions with multiple case clauses. If any case is satisfied with the expression, then the codes placed under that case clause will execute. The default statement or clause is executed whenever the expression does not match any case clauses. Using a switch without the default is possible, but it is always recommended to use the default statement to manage or handle any non-desired or unknown conditions.

switch (expression) {
   case value:
   
   // block of code under this case
   break;
   ...
   default:
   
   // block of code under this default
   break;
}

Use The Spread Operator (...)

In JavaScript, the spread operator is used to copy or replicate arrays or objects. As the array and objects are reference types, we can’t assign the whole array or object using the equals operator or copy an array. We need to use for loop or a while loop if we don’t use the spread operator. The spread operator reduces the codes and makes them easy to understand.

let arr1 = [1, 2, 3, 4, 5]

// using the spread operator
let arr2 = [...arr1]

Limit DOM Access

In JavaScript, accessing the DOM elements too much can cause huge performance issues. Also don’t use document.getElementById() or document.getElementByTagName() method too many times instead of that call these methods one time and storing the return types in a variable and using them. Create an output string and modify the element innerHTML at the end of the code.

let element = document.getElementById('element_id')
element.innerHTML = 'JavaScript'

Don’t Use The eval()

The eval() method in JavaScript compiles and executes a string of code statements. It is a very powerful tool but it also affects our code’s security and performance. It is recommended to don’t use the eval() until it is necessary.

Reduce The Loop Iteration

Loop iterations take time to complete, and it also needs to check certain conditions in each iteration. So it is always beneficial to have small loop iterations instead of long looping. Also, declare the loop variables before the loop starts to save more performance.

Use Asynchronous Programming

Asynchronous programming makes JavaScript more efficient. Whenever users are required to perform an HTTP request or other asynchronous operations, always use the async await in JavaScript.

Put Javascript Code At The Bottom Or In A Separate File

To use JavaScript code, the whole DOM must be loaded, so putting the JavaScript code at the bottom of the page helps run JavaScript code without any interruptions. Also, if the same JavaScript code is required on multiple pages or the JavaScript code becomes large, then it is better to put the JavaScript code in a separate file.