c) A scope where variables are accessible from anywhere in the code
d) A scope only within loops
Answer:
c) A scope where variables are accessible from anywhere in the code
Explanation:
Global scope refers to variables that are declared outside any function or block and are accessible from any part of the code.
2. What defines the function scope in JavaScript?
a) Variables declared within a function
b) Variables declared outside a function
c) Variables declared within a loop
d) Variables declared within a block
Answer:
a) Variables declared within a function
Explanation:
Function scope is defined by variables declared within a function. These variables are accessible only within the function and not outside it.
3. How does block scope work in JavaScript?
a) Variables are confined within a function
b) Variables are confined within a block of code, such as loops or conditionals
c) Variables are accessible globally
d) Variables are confined within the entire script
Answer:
b) Variables are confined within a block of code, such as loops or conditionals
Explanation:
Block scope means that variables declared within a block (e.g., within curly braces of if statements, loops) are only accessible within that block.
4. Which statement about let and const in JavaScript is true?
a) They create global scoped variables
b) They create function scoped variables
c) They create block scoped variables
d) They do not define scope
Answer:
c) They create block scoped variables
Explanation:
The let and const keywords in JavaScript declare variables that are block scoped, meaning they are only accessible within the block they are defined in.
5. What happens to a variable declared with var inside a function?
a) It becomes block scoped
b) It becomes globally scoped
c) It becomes function scoped
d) It is not scoped
Answer:
c) It becomes function scoped
Explanation:
Variables declared with var inside a function are function scoped, meaning they are accessible only within the function and not outside it.
6. Can a variable declared in a block with let be accessed outside of the block?
a) Yes, always
b) No, it is block scoped
c) Yes, but only within functions
d) Yes, but only in the global scope
Answer:
b) No, it is block scoped
Explanation:
Variables declared with let within a block cannot be accessed outside that block as they are block scoped.
7. What is a typical use case for block scope in JavaScript?
a) To keep variables global
b) To restrict access to variables within loops or conditional blocks
c) To create private functions
d) To create global constants
Answer:
b) To restrict access to variables within loops or conditional blocks
Explanation:
Block scope is typically used to restrict access to variables within certain blocks of code like loops or conditional statements for better control and to avoid conflicts.
8. What type of scope does the var keyword create in a loop in JavaScript?
a) Block scope
b) Function scope
c) Global scope
d) Loop scope
Answer:
b) Function scope
Explanation:
The var keyword, even when used in a loop, creates a function scope if the loop is within a function, and global scope if the loop is in the global context.
9. How does global scope affect variables in JavaScript?
a) It limits variable accessibility to specific functions
b) It restricts variable accessibility to specific blocks
c) It makes variables accessible from anywhere in the code
d) It makes variables immutable
Answer:
c) It makes variables accessible from anywhere in the code
Explanation:
Global scope allows variables to be accessible from any part of the code, regardless of blocks or functions.
10. What is the best practice regarding global scope in JavaScript?
a) Always use global scope for variables
b) Limit the use of global scope to avoid conflicts
c) Use global scope within functions only
d) Global scope should be used for all variables
Answer:
b) Limit the use of global scope to avoid conflicts
Explanation:
It is best practice to limit the use of global scope as it can lead to conflicts and difficulties in managing the code, especially in larger applications.
11. How are const and let different from var in terms of scope?
a) const and let are not scoped, while var is function scoped
b) const and let are block scoped, while var is function scoped
c) const and let are function scoped, while var is block scoped
d) const and let are global scoped, while var is not scoped
Answer:
b) const and let are block scoped, while var is function scoped
Explanation:
const and let provide block scope, which confines variables to the block where they are declared. var, however, is function scoped.
12. What is the outcome of using a variable outside its scope?
a) The code executes normally
b) A reference error is thrown
c) The variable automatically becomes global
d) The variable's value is set to undefined
Answer:
b) A reference error is thrown
Explanation:
Attempting to use a variable outside its scope results in a reference error because the variable is not accessible outside its defined scope.
13. Is it possible to access a block-scoped variable before its declaration?
a) Yes, always
b) Yes, but it returns undefined
c) No, it results in a reference error
d) No, but it can be hoisted
Answer:
c) No, it results in a reference error
Explanation:
Accessing a block-scoped variable (declared with let or const) before its declaration results in a ReferenceError due to the temporal dead zone.
14. What is the scope of a variable declared outside any function or block in JavaScript?
a) Function scope
b) Block scope
c) Local scope
d) Global scope
Answer:
d) Global scope
Explanation:
Variables declared outside any function or block have global scope, making them accessible from anywhere in the code.
15. Can a function access a variable in the scope of its calling function?
a) Yes, always
b) No, it's not possible
c) Only if the variable is global
d) Only if the variable is passed as an argument
Answer:
b) No, it's not possible
Explanation:
A function cannot access variables in the scope of its calling function unless those variables are passed to it as arguments or are in the global scope.