The **`equal`** method of the `assert` module in Node.js uses the `==` operator (Abstract Equality Comparison) to check for equality between two values.

The process is illustrated below:

>Note: You can view a list of rules for the `==` operator [here](https://tc39.es/ecma262/#sec-abstract-equality-comparison). 

To use the `equal` method, you will need to install the `assert` module using the command prompt as shown below:

```Javascript
npm install assert
```

After the installation is complete, you will need to import the `assert` module into the program as shown below:

```Java
const assert = require('assert');
```

The prototype of the `equal` method is shown below:

```Java
equal(actual, expected[, message])
```

# Parameters

The `equal` method takes the following parameters:

* **`actual`**: The first of the two values to compare.

* **`expected`**: The second of the two values to compare.

* **`message`**: This optional parameter holds the error message in case of an [AssertionError](https://nodejs.org/api/assert.html#assert_class_assert_assertionerror). If this parameter is left empty, a default message is assigned.

# Return value

If the values are not equal, then the `equal` method throws an [AssertionError](https://nodejs.org/api/assert.html#assert_class_assert_assertionerror), and the program terminates; otherwise, execution continues as normal.

In case of an error, the `message` property of the `AssertionError` is set equal to the `message` parameter. If the `message` parameter is not provided, a default value is assigned to the `message` property of the `AssertionError`. 

>Note: The `equal` method also handles `NaN`(Not-A-Number) comparisons. If both values are `NaN`, the `equal` method recognizes them as being identical.

# Example

The code below shows how the `equal` method works in Node.js:

const assert = require('assert');

// evaluating first expression
try{
  assert.equal(10, 10, "Assertion Error: The values are inequal.")
  console.log("No error.")
}
catch(error){
  console.log(error.message)
}

// evaluating second expression
try{
  assert.equal(10, "10", "Assertion Error: The values are inequal.")
  console.log("No error.")
}
catch(error){
  console.log(error.message)
}

// evaluating third expression
try{
  assert.equal(10, 5, "Assertion Error: The values are inequal.")
  console.log("No error.")
}
catch(error){
  console.log(error.message)
}

# Explanation

The code above uses $3$ different expressions to show the behavior of the `equal` method.

In the first expression in line $5$, the `actual` and `expected` parameters are both $10$, so the `equal` method does not throw any errors. Therefore, only the `try` branch of the `try-catch` block executes.

In the second expression in line $14$, the `actual` and `expected` parameters are again $10$, but they have different types. The `actual` parameter is an integer, whereas the `expected` parameter is a string. Since the `equal` method uses [abstract equality comparison rules](https://tc39.es/ecma262/#sec-abstract-equality-comparison), it considers the two values equal and does not throw any errors. Therefore, only the `try` branch of the `try-catch` block executes.

In the third expression in line $23$, the `actual` and `expected` parameters are unequal, so an error is thrown, which triggers the `catch` branch of the `try-catch` block. The code outputs the message associated with the error, i.e., the string provided as the `message` parameter to the `equal` method in line $23$.

What is the equal method of the assert module in Node.js?

The equal method in Node.js's assert module uses the == operator for equality checks, comparing two values with the option to include a custom error message.