Understanding Variable Value In JavaScript

In the provided code snippet, we're asking about the value of the JavaScript variable elem. To answer this question correctly, we need to discuss the concept of conditional statements in JavaScript, and more specifically the if...else statement.

In JavaScript, the if...else structure is used to execute one block of code if a specified condition is true and another block of code if it is false. In our case, the condition is 11 == 11 && 12 < 10.

Here, 11 == 11 will return true, because 11 is indeed equal to 11. However, 12 < 10 returns false, because 12 is not less than 10.

The && operator is a logical AND operator. It tests whether both expressions are true. If they are, it returns true; if not, it returns false. So in our scenario, we have one expression that is true and another that is false, as a result of which the whole condition becomes false.

Since the if condition failed, the code inside the if block is not executed. Rather, the code inside the else block is executed which is elem = "undefined".

That's why, after the code runs, the value of elem becomes 'undefined'.

Also, it's worth noting that the idea of setting a variable to the string "undefined" is not a typical approach in JavaScript. Usually, the JavaScript undefined value is used in such scenarios when a variable has been declared, but has not been assigned any value.

But in this case, elem is indeed assigned a value, a string value of "undefined", which can potentially cause confusion. So while this code is valid, it might not be seen as a best practice.

Here's an improved version of the code:

var elem;
if (11 == 11 && 12 < 10) {
  elem = 12;
} else {
  elem = undefined;
}

In the modified code, elem is assigned the undefined value, not a string "undefined". This makes our code less prone to confusion and clearer to fellow developers.

In summary, understanding JavaScript's conditional statements and logical operators is key to determining the value of variables in different circumstances. Being aware of these fundamentals allows you to write more effective and understandable code.