JavaScript is a versatile programming language widely used for web development. As with any programming language, there are certain habits that can indicate a developer's level of experience.

In this article, we will explore some common JavaScript habits that often give away inexperience and how they can be identified and corrected. By being aware of these habits, both novice and experienced developers can improve their skills and write more efficient, error-resilient, and maintainable code.

1. Not using Strict Mode:

   When we fail to use strict mode it leads to an implicit global variable declaration, which can cause unexpected behavior and naming conflicts within the codebase. Like in the example below the variable area is not explicitly declared using the var, let, or const keywords.

    function calculateArea(length, width) {
        area = length * width;
        return area;
    }
    // Using Strict 
    function calculateArea(length, width) {
        'use strict';
        let area = length * width;
        return area;
    }
   

   By including the 'use strict'; directive, we enable strict mode and ensure that variable declarations are explicit. In the corrected code, the area variable is properly declared using the let keyword, limiting its scope to the calculateArea function.

2. Global Variable Abuse:

    let counter = 0;
   
    function incrementCounter() {
        counter += 1;
    }
   
    function logCounter() {
        console.log(counter);
    }
   

   Inexperienced developers often rely on global variables, such as the counter variable in the above code. While it may work for small projects, excessive use of global variables can lead to naming conflicts and difficulties in maintaining and scaling the codebase.

   The correct way would be to encapsulate the counter within the createCounter function, effectively limiting its scope. The functions incrementCounter and logCounter are defined within the createCounter function and returned as an object. This approach allows for better organization, avoids global variable conflicts, and promotes modularity.

    function createCounter() {
        let counter = 0;
   
        function incrementCounter() {
            counter += 1;
        }
   
        function logCounter() {
            console.log(counter);
        }
   
        return {
            increment: incrementCounter,
            log: logCounter
        };
    }
   
    const counter = createCounter();
    counter.increment();
    counter.log();
   

3. Lack Of Error Handling

    function divide(a, b) {
        return a / b;
    }
   
    const result = divide(10, 0);
    console.log(result);
   

   The above code does not handle the scenario when dividing by zero. Most developers often overlook proper error handling, leading to uncaught exceptions and unexpected application crashes.

   The correct way would be for example to use an if else statement where the if statement checks if the divisor (b) is zero before performing the division. If it is, an Error is thrown with a descriptive message. The division is wrapped in a try-catch block to catch the exception and handle it gracefully, printing an error message to the console.

function divide(a, b) {
    if (b === 0) {
        throw new Error('Cannot divide by zero.');
    }
    return a / b;
}

try {
    const result = divide(10, 0);
    console.log(result);
} catch (error) {
    console.error(error);
}

1. Ignoring Asynchronous Programming:

   A common mistake that is often made by developers, is when we treat asynchronous operations as if they were synchronous. The fetch API returns a promise, and the response data is assigned to the data variable. However, due to the asynchronous nature of the fetch operation, the return data statement executes before the promise is resolved, resulting in an undefined return value.

    function fetchData(url) {
        let data;
        fetch(url)
            .then(response => response.json())
            .then(result => {
                data = result;
            });
        return data;
    }
   
    //Asynchronous function
    async function fetchData(url) {
        const response = await fetch(url);
        const data = await response.json();
        return data;
    }
   

   A common mistake that is often made by developers, is when we treat asynchronous operations as if they were synchronous. The fetch API returns a promise, and the response data is assigned to the data variable. However, due to the asynchronous nature of the fetch operation, the return data statement executes before the promise is resolved, resulting in an undefined return value.

   By utilizing async/await, the await keyword ensures that the function waits for the promise to resolve before proceeding, allowing the data to be assigned correctly and returned.

2. Use == instead of ===:

    let num = 5;
    let strNum = "5";
   
    if (num == strNum) {
        console.log("Equal");
    } else {
        console.log("Not equal");
    }
   

   The loose equality operator performs type coercion, which can lead to unexpected results. In the above example, the comparison num == strNum evaluates to true because the loose equality operator converts the string "5" to a number before comparing. This can introduce subtle bugs and make code harder to reason about.

    let num = 5;
    let strNum = "5";
   
    if (num === parseInt(strNum)) {
        console.log("Equal");
    } else {
        console.log("Not equal");
    }
   

   Using the strict equality operator === and explicitly converting the string to a number using parseInt(). This ensures that the comparison is done based on both value and type, providing more predictable and reliable behavior.

3. Manual String Formatting:

   Concatenating strings manually using the + operator, resulting in less readable and error-prone code. This approach becomes especially problematic when dealing with complex string formatting requirements.

    let firstName = "John";
    let lastName = "Doe";
   
    let fullName = firstName + " " + lastName;
    console.log("Full Name: " + fullName);
   
    //Using template literals
    let firstName = "John";
    let lastName = "Doe";
   
    let fullName = `${firstName} ${lastName}`;
    console.log(`Full Name: ${fullName}`);
   

   The correct way is to utilize template literals (delimited by backticks) to format strings. Template literals allow for easy variable interpolation and multiline strings, improving code readability and maintainability.

4. Traditional for loop:

Using traditional for loop and Object.keys() to iterate over the keys of an object is inefficient and unnecessary since JavaScript provides more straightforward alternatives.

Using a for...in loop iterates directly over the keys of the object. This approach simplifies the code and improves performance by avoiding unnecessary function calls. Additionally, using user[key] like in the example below allows us to access the corresponding value associated with each key in the object.

let user = {
    name: "John",
    age: 30,
    profession: "Developer"
};

for (let i = 0; i < Object.keys(user).length; i++) {
    let key = Object.keys(user)[i];
    console.log(key + ": " + user[key]);
}

//Using for ... in
let user = {
    name: "John",
    age: 30,
    profession: "Developer"
};

for (let key in user) {
    console.log(key + ": " + user[key]);
}

Conclusion

I believe by recognizing and addressing these common habits that give away inexperience in JavaScript development, developers can enhance their skills especially those who are new in the language and want to write more efficient and maintainable code.