A function definition expression, also known as a function literal, is a way to define a function in JavaScript.
It consists of the function keyword, followed by a list of parameters inside parentheses,
and a block of code inside curly braces that defines the function's behavior.
Here's an example of a function definition expression:
let greet = function(name) {
console.log('Hello, ' + name);
};

This function definition expression defines a function called greet that takes a single parameter called name and logs a greeting to the console.

arr[3] is the correct way to access the third element in an array arr.
In JavaScript, you can use square brackets ([]) to access elements in an array by their index.
The index of the first element in an array is 0,
so to access the third element, you would use an index of 2.

The subset excludes the comma operator, bitwise operators, and the ++ and — operators.
Additionally, it requires the use of == and!= instead of == and!= owing to the type conversion that they do.

In JavaScript, if a local variable and a global variable have the same name, the local variable takes precedence over the global variable.
Here's an example of how this works:
let x = 5; // x is a global variable
function foo() {
let x = 10; // x is a local variable
console.log(x); // Output: 10
}

foo(); // Output: 10
console.log(x); // Output: 5
In this example, the local variable x is defined within the foo function, and it takes precedence over the global variable x.
When we log the value of x within the function, it prints 10, which is the value of the local variable.
When we log the value of x outside the function, it
prints 5, which is the value of the global variable.

This is known as variable shadowing,
and it occurs when a local variable with the same name as a global variable "shadows" the global variable, hiding it from view within the local scope.

You can use the javascript: protocol in a URL to execute a JavaScript function.
This can be used, for example, to create a link that executes a JavaScript function when clicked.

The === operator is known as the strict equality operator in JavaScript.
It is used to test whether two values are equal, and it returns true if the values are equal and their types are the same.

For example:
console.log(1 === 1); // Output: true
console.log('1' === 1); // Output: false

In the first example, the === operator returns true because both operands are equal and have the same type (number).
In the second example, the === operator returns false because although the operands are equal in value, they have different types (string and number).
The strict equality operator is often used as an alternative to the == operator, which is known as the abstract equality operator.
The == operator performs type coercion, which means it converts the operands to the same type before making the comparison.
This can lead to unexpected results in some cases, so the === operator is generally considered a safer choice.

in is not a logical operator in JavaScript.
Logical operators in JavaScript include && (and), || (or), and ! (not).
in is an operator that is used to check whether an object has a property with a given name.

The substr() method extracts a specified number of characters from a string,
starting at a specified index position.
Here's an example of how to use it:
let str = 'Hello World';
let sub = str.substr(6, 5); // Extract 5 characters starting at index 6
console.log(sub); // Output: "World"
The substr() method is similar to the substring() method, which also extracts characters from a string.
The main difference between the two is that substring() does not allow negative indexes, whereas substr() does.

Global variables are variables that are defined outside of any function or block of code.
They have global scope, which means that they are visible and can be accessed from anywhere in your code.

Here's an example of how to define a global variable in JavaScript:
let x = 5; // x is a global variable
function foo() {
console.log(x); // x is visible and can be accessed from within the function
}

foo(); // Output: 5

It is generally considered a best practice to avoid using global variables in your code,
as they can lead to conflicts and make your code harder to maintain. Instead, it is usually better to use local variables that are defined within a function or block of code,
and to pass data between functions as arguments and return values.

The result of the code is false.
The === operator in JavaScript performs a strict comparison, which means that it not only checks for equality,
but also checks for type equality.
In this case, the operands x and y have different types (one is a number and the other is a string), so the comparison returns false.