Understanding the Not Equals Operator in JavaScript

What is the Not Equals Operator in JavaScript?

The not equals operator in JavaScript is used to check if two values are not equal. There are two types of not equals operators in JavaScript:

1. Loose Inequality (!=): This operator compares the values after performing type coercion. If the values are not equal, it returns true; otherwise, it returns false.

2. Strict Inequality (!==): This operator compares both the value and the type of the operands. If either the value or the type is different, it returns true; otherwise, it returns false.

Loose Inequality (!=)

The != operator is used to check if two values are not equal, but it does not check the type. It converts both operands to the same type before comparison.

Example 1:

let a = 5;
let b = "5";

console.log(a != b); // Output: false

In this example, a is a number and b is a string. The != operator converts b to a number before comparison. Since both values are equal after conversion, it returns false.

Example 2:

let x = 10;
let y = "10";

console.log(x != y); // Output: false

Strict Inequality (!==)

The !== operator checks both the value and the type of the operands. If either the value or the type is different, it returns true.

Example 1:

let a = 5;
let b = "5";

console.log(a !== b); // Output: true

Here, a is a number and b is a string. Since the types are different, !== returns true.

Example 2:

let x = 10;
let y = "10";

console.log(x !== y); // Output: true

Common Use Cases

1. Form Validation: Checking if a user input is not empty or not equal to a specific value.

let userInput = document.getElementById("username").value;

if (userInput !== "") {
  console.log("Username is valid.");
} else {
  console.log("Username cannot be empty.");
}

1. Conditional Statements: Using != or !== to control the flow of the program based on certain conditions.

let age = 18;

if (age != 21) {
  console.log("You are not 21 years old.");
}

1. Data Validation: Ensuring that a variable does not hold a specific value before proceeding with an operation.

let result = null;

if (result !== null) {
  console.log("Result is available.");
} else {
  console.log("Result is not available yet.");
}

Frequently Asked Questions

1. What is the difference between != and !==?

• != checks for inequality after performing type coercion.
• !== checks for inequality without performing type coercion, considering both value and type.

2. When should I use != instead of !==?

Use != when you want to compare values without worrying about their types. However, it’s generally recommended to use !== to avoid unexpected results due to type coercion.

3. Can I use the not equals operator with objects?

Yes, but it will only check if the objects are the same object in memory, not if their contents are equal. For example:

let obj1 = { name: "John" };
let obj2 = { name: "John" };

console.log(obj1 != obj2); // Output: false
console.log(obj1 !== obj2); // Output: true

4. How does the not equals operator handle null and undefined?

• null == undefined returns true, so null != undefined returns false.
• null === undefined returns false, so null !== undefined returns true.

5. What happens if I use the not equals operator with different data types?

The != operator converts both operands to the same type before comparison, while !== does not perform any conversion.

Best Practices

1. Use !== for Strict Comparisons: Always prefer !== when you want to ensure both value and type are different.

2. Understand Type Coercion: Be aware of how JavaScript converts types when using != to avoid unexpected results.

3. Test Your Code: Always test your code with different data types and values to ensure the not equals operator behaves as expected.

By understanding the differences between != and !==, you can write more accurate and reliable JavaScript code.