In JavaScript, var is a way to declare variables, but it behaves differently than let and const. The main issue with var is its scope: it's function-scoped, meaning it's visible throughout the entire function it's declared in, or globally if declared outside any function. This can lead to unexpected behavior, especially in large codebases, because variables declared with var can be accidentally overwritten or accessed from unintended parts of your code. Modern JavaScript favors let and const, which offer block scoping, limiting the visibility of variables to the block of code where they are defined (usually within curly braces {}). Using let and const helps prevent common errors and makes code easier to understand and maintain.
Match the term with its definition:
| Term | Definition |
|---|---|
| 1. Scope | A. A variable declaration with function scope |
| 2. Block Scoping | B. The portion of the code where a variable is accessible |
| 3. var | C. Introduces a variable that cannot be reassigned after initialization |
| 4. let | D. Limits the visibility of variables to the block of code where they're defined. |
| 5. const | E. Declares a block-scoped local variable, optionally initializing it to a value. |
(Answers: 1-B, 2-D, 3-A, 4-E, 5-C)
__________ and __________ are preferred over __________ in modern JavaScript because they provide __________ scoping, which helps prevent accidental variable __________ and makes code easier to __________.
(Answers: let, const, var, block, overwriting, maintain)
Explain a scenario where using var might unintentionally cause a bug in your JavaScript code and how using let or const could prevent it.
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