Explain the purpose of the !== operator in JavaScript.

The `!==` operator in JavaScript is the "strict inequality" operator. It is used to compare two values for both value and type inequality. In other words, it returns `true` if the values are not equal or if they are of different types, and `false` if the values are equal and of the same type.

The `!==` operator is the negation of the `===` operator, which is the strict equality operator. While `===` checks for both value and type equality, `!==` checks for value or type inequality.

Here's an example to illustrate the use of `!==`:

let num1 = 5;

let num2 = "5";

if (num1 !== num2) {

    console.log("Values or types are not equal.");

} else {

    console.log("Values and types are equal.");

}

In this example, even though the values of `num1` and `num2` are the same, they have different types (number and string). Therefore, the condition `num1 !== num2` evaluates to `true`, and the message "Values or types are not equal." will be logged to the console.

Using `!==` is a way to ensure strict comparison, considering both the values and their types. It's generally recommended to use strict equality and inequality (`===` and `!==`) when comparing values in JavaScript to avoid unexpected type coercion that can occur with loose equality (`==` and `!=`).