JavaScript
/Beginner
Variables (var, let, const)
Definition
Variables are containers for storing data values. In JavaScript, you can declare them using var, let, or const. They determine how the stored data can be accessed and if it can be changed.
Explain Like I'm New
Think of variables like labeled boxes. You put something inside the box, and you can find it later by looking for the label. 'let' is a box whose contents you can change. 'const' is a locked box where the contents cannot be swapped out. 'var' is an older type of box that behaves a bit unpredictably.
Real World Example
When playing a video game, your 'score' is a variable that changes (like 'let'), while your 'maxHealth' might be a fixed value that never changes (like 'const').
Common Use Cases
- •Storing user input
- •Keeping track of application state (e.g., is user logged in?)
- •Holding configuration values that never change
Interactive Example
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Interview Questions
basic
- What is the difference between let, const, and var?
- Can you reassign a const variable?
intermediate
- What does 'block scope' mean for let and const?
- Can you mutate an object or array declared with const?
advanced
- What is the Temporal Dead Zone (TDZ)?
- How does the JavaScript engine handle variable declarations during the creation phase?
trick
- If you declare a variable without a keyword inside a function, what happens?